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perlfunc (1)
  • >> perlfunc (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • perlfunc (1) ( Разные man: Команды и прикладные программы пользовательского уровня )
  • 
    
    

    NAME

         perlfunc - Perl builtin functions
    
    
    

    DESCRIPTION

         The functions in this section can serve as terms in an
         expression.  They fall into two major categories: list
         operators and named unary operators.  These differ in their
         precedence relationship with a following comma.  (See the
         precedence table in the perlop manpage.)  List operators
         take more than one argument, while unary operators can never
         take more than one argument.  Thus, a comma terminates the
         argument of a unary operator, but merely separates the
         arguments of a list operator.  A unary operator generally
         provides a scalar context to its argument, while a list
         operator may provide either scalar or list contexts for its
         arguments.  If it does both, the scalar arguments will be
         first, and the list argument will follow.  (Note that there
         can ever be only one such list argument.)  For instance,
         splice() has three scalar arguments followed by a list,
         whereas gethostbyname() has four scalar arguments.
    
         In the syntax descriptions that follow, list operators that
         expect a list (and provide list context for the elements of
         the list) are shown with LIST as an argument.  Such a list
         may consist of any combination of scalar arguments or list
         values; the list values will be included in the list as if
         each individual element were interpolated at that point in
         the list, forming a longer single-dimensional list value.
         Elements of the LIST should be separated by commas.
    
         Any function in the list below may be used either with or
         without parentheses around its arguments.  (The syntax
         descriptions omit the parentheses.)  If you use the
         parentheses, the simple (but occasionally surprising) rule
         is this: It looks like a function, therefore it is a
         function, and precedence doesn't matter.  Otherwise it's a
         list operator or unary operator, and precedence does matter.
         And whitespace between the function and left parenthesis
         doesn't count--so you need to be careful sometimes:
    
             print 1+2+4;        # Prints 7.
             print(1+2) + 4;     # Prints 3.
             print (1+2)+4;      # Also prints 3!
             print +(1+2)+4;     # Prints 7.
             print ((1+2)+4);    # Prints 7.
    
         If you run Perl with the -w switch it can warn you about
         this.  For example, the third line above produces:
    
             print (...) interpreted as function at - line 1.
             Useless use of integer addition in void context at - line 1.
    
         A few functions take no arguments at all, and therefore work
         as neither unary nor list operators.  These include such
         functions as `time' and `endpwent'.  For example,
         `time+86_400' always means `time() + 86_400'.
    
         For functions that can be used in either a scalar or list
         context, nonabortive failure is generally indicated in a
         scalar context by returning the undefined value, and in a
         list context by returning the null list.
    
         Remember the following important rule: There is no rule that
         relates the behavior of an expression in list context to its
         behavior in scalar context, or vice versa.  It might do two
         totally different things.  Each operator and function
         decides which sort of value it would be most appropriate to
         return in scalar context.  Some operators return the length
         of the list that would have been returned in list context.
         Some operators return the first value in the list.  Some
         operators return the last value in the list.  Some operators
         return a count of successful operations.  In general, they
         do what you want, unless you want consistency.
    
         An named array in scalar context is quite different from
         what would at first glance appear to be a list in scalar
         context.  You can't get a list like `(1,2,3)' into being in
         scalar context, because the compiler knows the context at
         compile time.  It would generate the scalar comma operator
         there, not the list construction version of the comma.  That
         means it was never a list to start with.
    
         In general, functions in Perl that serve as wrappers for
         system calls of the same name (like chown(2), fork(2),
         closedir(2), etc.) all return true when they succeed and
         `undef' otherwise, as is usually mentioned in the
         descriptions below.  This is different from the C
         interfaces, which return `-1' on failure.  Exceptions to
         this rule are `wait', `waitpid', and `syscall'.  System
         calls also set the special `$!'  variable on failure.  Other
         functions do not, except accidentally.
    
         Perl Functions by Category
    
         Here are Perl's functions (including things that look like
         functions, like some keywords and named operators) arranged
         by category.  Some functions appear in more than one place.
    
         Functions for SCALARs or strings
             `chomp', `chop', `chr', `crypt', `hex', `index', `lc',
             `lcfirst', `length', `oct', `ord', `pack', `q/STRING/',
             `qq/STRING/', `reverse', `rindex', `sprintf', `substr',
             `tr///', `uc', `ucfirst', `y///'
    
         Regular expressions and pattern matching
             `m//', `pos', `quotemeta', `s///', `split', `study',
             `qr//'
    
         Numeric functions
             `abs', `atan2', `cos', `exp', `hex', `int', `log',
             `oct', `rand', `sin', `sqrt', `srand'
    
         Functions for real @ARRAYs
             `pop', `push', `shift', `splice', `unshift'
    
         Functions for list data
             `grep', `join', `map', `qw/STRING/', `reverse', `sort',
             `unpack'
    
         Functions for real %HASHes
             `delete', `each', `exists', `keys', `values'
    
         Input and output functions
             `binmode', `close', `closedir', `dbmclose', `dbmopen',
             `die', `eof', `fileno', `flock', `format', `getc',
             `print', `printf', `read', `readdir', `rewinddir',
             `seek', `seekdir', `select', `syscall', `sysread',
             `sysseek', `syswrite', `tell', `telldir', `truncate',
             `warn', `write'
    
         Functions for fixed length data or records
             `pack', `read', `syscall', `sysread', `syswrite',
             `unpack', `vec'
    
         Functions for filehandles, files, or directories
             `-X', `chdir', `chmod', `chown', `chroot', `fcntl',
             `glob', `ioctl', `link', `lstat', `mkdir', `open',
             `opendir', `readlink', `rename', `rmdir', `stat',
             `symlink', `umask', `unlink', `utime'
    
         Keywords related to the control flow of your perl program
             `caller', `continue', `die', `do', `dump', `eval',
             `exit', `goto', `last', `next', `redo', `return', `sub',
             `wantarray'
    
         Keywords related to scoping
             `caller', `import', `local', `my', `package', `use'
    
         Miscellaneous functions
             `defined', `dump', `eval', `formline', `local', `my',
             `reset', `scalar', `undef', `wantarray'
    
         Functions for processes and process groups
             `alarm', `exec', `fork', `getpgrp', `getppid',
             `getpriority', `kill', `pipe', `qx/STRING/', `setpgrp',
             `setpriority', `sleep', `system', `times', `wait',
             `waitpid'
    
         Keywords related to perl modules
             `do', `import', `no', `package', `require', `use'
    
         Keywords related to classes and object-orientedness
             `bless', `dbmclose', `dbmopen', `package', `ref', `tie',
             `tied', `untie', `use'
    
         Low-level socket functions
             `accept', `bind', `connect', `getpeername',
             `getsockname', `getsockopt', `listen', `recv', `send',
             `setsockopt', `shutdown', `socket', `socketpair'
    
         System V interprocess communication functions
             `msgctl', `msgget', `msgrcv', `msgsnd', `semctl',
             `semget', `semop', `shmctl', `shmget', `shmread',
             `shmwrite'
    
         Fetching user and group info
             `endgrent', `endhostent', `endnetent', `endpwent',
             `getgrent', `getgrgid', `getgrnam', `getlogin',
             `getpwent', `getpwnam', `getpwuid', `setgrent',
             `setpwent'
    
         Fetching network info
             `endprotoent', `endservent', `gethostbyaddr',
             `gethostbyname', `gethostent', `getnetbyaddr',
             `getnetbyname', `getnetent', `getprotobyname',
             `getprotobynumber', `getprotoent', `getservbyname',
             `getservbyport', `getservent', `sethostent',
             `setnetent', `setprotoent', `setservent'
    
         Time-related functions
             `gmtime', `localtime', `time', `times'
    
         Functions new in perl5
             `abs', `bless', `chomp', `chr', `exists', `formline',
             `glob', `import', `lc', `lcfirst', `map', `my', `no',
             `prototype', `qx', `qw', `readline', `readpipe', `ref',
             `sub*', `sysopen', `tie', `tied', `uc', `ucfirst',
             `untie', `use'
    
             * - `sub' was a keyword in perl4, but in perl5 it is an
             operator, which can be used in expressions.
    
         Functions obsoleted in perl5
             `dbmclose', `dbmopen'
    
    
    
         Portability
    
         Perl was born in Unix and can therefore access all common
         Unix system calls.  In non-Unix environments, the
         functionality of some Unix system calls may not be
         available, or details of the available functionality may
         differ slightly.  The Perl functions affected by this are:
    
         `-X', `binmode', `chmod', `chown', `chroot', `crypt',
         `dbmclose', `dbmopen', `dump', `endgrent', `endhostent',
         `endnetent', `endprotoent', `endpwent', `endservent',
         `exec', `fcntl', `flock', `fork', `getgrent', `getgrgid',
         `gethostent', `getlogin', `getnetbyaddr', `getnetbyname',
         `getnetent', `getppid', `getprgp', `getpriority',
         `getprotobynumber', `getprotoent', `getpwent', `getpwnam',
         `getpwuid', `getservbyport', `getservent', `getsockopt',
         `glob', `ioctl', `kill', `link', `lstat', `msgctl',
         `msgget', `msgrcv', `msgsnd', `open', `pipe', `readlink',
         `rename', `select', `semctl', `semget', `semop', `setgrent',
         `sethostent', `setnetent', `setpgrp', `setpriority',
         `setprotoent', `setpwent', `setservent', `setsockopt',
         `shmctl', `shmget', `shmread', `shmwrite', `socket',
         `socketpair', `stat', `symlink', `syscall', `sysopen',
         `system', `times', `truncate', `umask', `unlink', `utime',
         `wait', `waitpid'
    
         For more information about the portability of these
         functions, see the perlport manpage and other available
         platform-specific documentation.
    
         Alphabetical Listing of Perl Functions
    
         -X FILEHANDLE
    
         -X EXPR
    
         -X      A file test, where X is one of the letters listed
                 below.  This unary operator takes one argument,
                 either a filename or a filehandle, and tests the
                 associated file to see if something is true about
                 it.  If the argument is omitted, tests `$_', except
                 for `-t', which tests STDIN.  Unless otherwise
                 documented, it returns `1' for true and `''' for
                 false, or the undefined value if the file doesn't
                 exist.  Despite the funny names, precedence is the
                 same as any other named unary operator, and the
                 argument may be parenthesized like any other unary
                 operator.  The operator may be any of:
    
    
    
                     -r  File is readable by effective uid/gid.
                     -w  File is writable by effective uid/gid.
                     -x  File is executable by effective uid/gid.
                     -o  File is owned by effective uid.
    
                     -R  File is readable by real uid/gid.
                     -W  File is writable by real uid/gid.
                     -X  File is executable by real uid/gid.
                     -O  File is owned by real uid.
    
                     -e  File exists.
                     -z  File has zero size.
                     -s  File has nonzero size (returns size).
    
                     -f  File is a plain file.
                     -d  File is a directory.
                     -l  File is a symbolic link.
                     -p  File is a named pipe (FIFO), or Filehandle is a pipe.
                     -S  File is a socket.
                     -b  File is a block special file.
                     -c  File is a character special file.
                     -t  Filehandle is opened to a tty.
    
                     -u  File has setuid bit set.
                     -g  File has setgid bit set.
                     -k  File has sticky bit set.
    
                     -T  File is an ASCII text file.
                     -B  File is a "binary" file (opposite of -T).
    
                     -M  Age of file in days when script started.
                     -A  Same for access time.
                     -C  Same for inode change time.
    
                 Example:
    
                     while (<>) {
                         chop;
                         next unless -f $_;      # ignore specials
                         #...
                     }
    
                 The interpretation of the file permission operators
                 `-r', `-R', `-w', `-W', `-x', and `-X' is by default
                 based solely on the mode of the file and the uids
                 and gids of the user.  There may be other reasons
                 you can't actually read, write, or execute the file.
                 Such reasons may be for example network filesystem
                 access controls, ACLs (access control lists), read-
                 only filesystems, and unrecognized executable
                 formats.
    
                 Also note that, for the superuser on the local
                 filesystems, the `-r', `-R', `-w', and `-W' tests
                 always return 1, and `-x' and `-X' return 1 if any
                 execute bit is set in the mode.  Scripts run by the
                 superuser may thus need to do a stat() to determine
                 the actual mode of the file, or temporarily set
                 their effective uid to something else.
    
                 If you are using ACLs, there is a pragma called
                 `filetest' that may produce more accurate results
                 than the bare stat() mode bits.  When under the `use
                 filetest 'access'' the above-mentioned filetests
                 will test whether the permission can (not) be
                 granted using the access() family of system calls.
                 Also note that the `-x' and `-X' may under this
                 pragma return true even if there are no execute
                 permission bits set (nor any extra execute
                 permission ACLs).  This strangeness is due to the
                 underlying system calls' definitions.  Read the
                 documentation for the `filetest' pragma for more
                 information.
    
                 Note that `-s/a/b/' does not do a negated
                 substitution.  Saying `-exp($foo)' still works as
                 expected, however--only single letters following a
                 minus are interpreted as file tests.
    
                 The `-T' and `-B' switches work as follows.  The
                 first block or so of the file is examined for odd
                 characters such as strange control codes or
                 characters with the high bit set.  If too many
                 strange characters (>30%) are found, it's a `-B'
                 file, otherwise it's a `-T' file.  Also, any file
                 containing null in the first block is considered a
                 binary file.  If `-T' or `-B' is used on a
                 filehandle, the current stdio buffer is examined
                 rather than the first block.  Both `-T' and `-B'
                 return true on a null file, or a file at EOF when
                 testing a filehandle.  Because you have to read a
                 file to do the `-T' test, on most occasions you want
                 to use a `-f' against the file first, as in `next
                 unless -f $file && -T $file'.
    
                 If any of the file tests (or either the `stat' or
                 `lstat' operators) are given the special filehandle
                 consisting of a solitary underline, then the stat
                 structure of the previous file test (or stat
                 operator) is used, saving a system call.  (This
                 doesn't work with `-t', and you need to remember
                 that lstat() and `-l' will leave values in the stat
                 structure for the symbolic link, not the real file.)
                 Example:
                     print "Can do.\n" if -r $a || -w _ || -x _;
    
                     stat($filename);
                     print "Readable\n" if -r _;
                     print "Writable\n" if -w _;
                     print "Executable\n" if -x _;
                     print "Setuid\n" if -u _;
                     print "Setgid\n" if -g _;
                     print "Sticky\n" if -k _;
                     print "Text\n" if -T _;
                     print "Binary\n" if -B _;
    
    
         abs VALUE
    
         abs     Returns the absolute value of its argument.  If
                 VALUE is omitted, uses `$_'.
    
         accept NEWSOCKET,GENERICSOCKET
                 Accepts an incoming socket connect, just as the
                 accept(2) system call does.  Returns the packed
                 address if it succeeded, false otherwise.  See the
                 example in the Sockets: Client/Server Communication
                 entry in the perlipc manpage.
    
                 On systems that support a close-on-exec flag on
                 files, the flag will be set for the newly opened
                 file descriptor, as determined by the value of $^F.
                 See the section on "$^F" in the perlvar manpage.
    
         alarm SECONDS
    
         alarm   Arranges to have a SIGALRM delivered to this process
                 after the specified number of seconds have elapsed.
                 If SECONDS is not specified, the value stored in
                 `$_' is used. (On some machines, unfortunately, the
                 elapsed time may be up to one second less than you
                 specified because of how seconds are counted.)  Only
                 one timer may be counting at once.  Each call
                 disables the previous timer, and an argument of `0'
                 may be supplied to cancel the previous timer without
                 starting a new one.  The returned value is the
                 amount of time remaining on the previous timer.
    
                 For delays of finer granularity than one second, you
                 may use Perl's four-argument version of select()
                 leaving the first three arguments undefined, or you
                 might be able to use the `syscall' interface to
                 access setitimer(2) if your system supports it.  The
                 Time::HiRes module from CPAN may also prove useful.
    
                 It is usually a mistake to intermix `alarm' and
                 `sleep' calls.  (`sleep' may be internally
                 implemented in your system with `alarm')
    
                 If you want to use `alarm' to time out a system call
                 you need to use an `eval'/`die' pair.  You can't
                 rely on the alarm causing the system call to fail
                 with `$!' set to `EINTR' because Perl sets up signal
                 handlers to restart system calls on some systems.
                 Using `eval'/`die' always works, modulo the caveats
                 given in the Signals entry in the perlipc manpage.
    
                     eval {
                         local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
                         alarm $timeout;
                         $nread = sysread SOCKET, $buffer, $size;
                         alarm 0;
                     };
                     if ($@) {
                         die unless $@ eq "alarm\n";   # propagate unexpected errors
                         # timed out
                     }
                     else {
                         # didn't
                     }
    
    
         atan2 Y,X
                 Returns the arctangent of Y/X in the range -pi to
                 pi.
    
                 For the tangent operation, you may use the
                 `Math::Trig::tan' function, or use the familiar
                 relation:
    
                     sub tan { sin($_[0]) / cos($_[0])  }
    
    
         bind SOCKET,NAME
                 Binds a network address to a socket, just as the
                 bind system call does.  Returns true if it
                 succeeded, false otherwise.  NAME should be a packed
                 address of the appropriate type for the socket.  See
                 the examples in the Sockets: Client/Server
                 Communication entry in the perlipc manpage.
    
         binmode FILEHANDLE, DISCIPLINE
    
         binmode FILEHANDLE
                 Arranges for FILEHANDLE to be read or written in
                 "binary" or "text" mode on systems where the run-
                 time libraries distinguish between binary and text
                 files.  If FILEHANDLE is an expression, the value is
                 taken as the name of the filehandle.  DISCIPLINE can
                 be either of `":raw"' for binary mode or `":crlf"'
                 for "text" mode.  If the DISCIPLINE is omitted, it
                 defaults to `":raw"'.
    
                 binmode() should be called after open() but before
                 any I/O is done on the filehandle.
    
                 On many systems binmode() currently has no effect,
                 but in future, it will be extended to support user-
                 defined input and output disciplines.  On some
                 systems binmode() is necessary when you're not
                 working with a text file.  For the sake of
                 portability it is a good idea to always use it when
                 appropriate, and to never use it when it isn't
                 appropriate.
    
                 In other words:  Regardless of platform, use
                 binmode() on binary files, and do not use binmode()
                 on text files.
    
                 The `open' pragma can be used to establish default
                 disciplines.  See the open manpage.
    
                 The operating system, device drivers, C libraries,
                 and Perl run-time system all work together to let
                 the programmer treat a single character (`\n') as
                 the line terminator, irrespective of the external
                 representation.  On many operating systems, the
                 native text file representation matches the internal
                 representation, but on some platforms the external
                 representation of `\n' is made up of more than one
                 character.
    
                 Mac OS and all variants of Unix use a single
                 character to end each line in the external
                 representation of text (even though that single
                 character is not necessarily the same across these
                 platforms).  Consequently binmode() has no effect on
                 these operating systems.  In other systems like VMS,
                 MS-DOS and the various flavors of MS-Windows your
                 program sees a `\n' as a simple `\cJ', but what's
                 stored in text files are the two characters
                 `\cM\cJ'.  That means that, if you don't use
                 binmode() on these systems, `\cM\cJ' sequences on
                 disk will be converted to `\n' on input, and any
                 `\n' in your program will be converted back to
                 `\cM\cJ' on output.  This is what you want for text
                 files, but it can be disastrous for binary files.
    
                 Another consequence of using binmode() (on some
                 systems) is that special end-of-file markers will be
                 seen as part of the data stream.  For systems from
                 the Microsoft family this means that if your binary
                 data contains `\cZ', the I/O subsystem will ragard
                 it as the end of the file, unless you use binmode().
    
                 binmode() is not only important for readline() and
                 print() operations, but also when using read(),
                 seek(), sysread(), syswrite() and tell() (see the
                 perlport manpage for more details).  See the `$/'
                 and `$\' variables in the perlvar manpage for how to
                 manually set your input and output line-termination
                 sequences.
    
         bless REF,CLASSNAME
    
         bless REF
                 This function tells the thingy referenced by REF
                 that it is now an object in the CLASSNAME package.
                 If CLASSNAME is omitted, the current package is
                 used.  Because a `bless' is often the last thing in
                 a constructor, it returns the reference for
                 convenience.  Always use the two-argument version if
                 the function doing the blessing might be inherited
                 by a derived class.  See the perltoot manpage and
                 the perlobj manpage for more about the blessing (and
                 blessings) of objects.
    
                 Consider always blessing objects in CLASSNAMEs that
                 are mixed case.  Namespaces with all lowercase names
                 are considered reserved for Perl pragmata.  Builtin
                 types have all uppercase names, so to prevent
                 confusion, you may wish to avoid such package names
                 as well.  Make sure that CLASSNAME is a true value.
    
                 See the Perl Modules entry in the perlmod manpage.
    
         caller EXPR
    
         caller  Returns the context of the current subroutine call.
                 In scalar context, returns the caller's package name
                 if there is a caller, that is, if we're in a
                 subroutine or `eval' or `require', and the undefined
                 value otherwise.  In list context, returns
    
                     ($package, $filename, $line) = caller;
    
                 With EXPR, it returns some extra information that
                 the debugger uses to print a stack trace.  The value
                 of EXPR indicates how many call frames to go back
                 before the current one.
    
    
                     ($package, $filename, $line, $subroutine, $hasargs,
                     $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i);
    
                 Here $subroutine may be `(eval)' if the frame is not
                 a subroutine call, but an `eval'.  In such a case
                 additional elements $evaltext and `$is_require' are
                 set: `$is_require' is true if the frame is created
                 by a `require' or `use' statement, $evaltext
                 contains the text of the `eval EXPR' statement.  In
                 particular, for a `eval BLOCK' statement, $filename
                 is `(eval)', but $evaltext is undefined.  (Note also
                 that each `use' statement creates a `require' frame
                 inside an `eval EXPR') frame.  `$hints' and
                 `$bitmask' contain pragmatic hints that the caller
                 was compiled with.  The `$hints' and `$bitmask'
                 values are subject to change between versions of
                 Perl, and are not meant for external use.
    
                 Furthermore, when called from within the DB package,
                 caller returns more detailed information: it sets
                 the list variable `@DB::args' to be the arguments
                 with which the subroutine was invoked.
    
                 Be aware that the optimizer might have optimized
                 call frames away before `caller' had a chance to get
                 the information.  That means that `caller(N)' might
                 not return information about the call frame you
                 expect it do, for `N > 1'.  In particular,
                 `@DB::args' might have information from the previous
                 time `caller' was called.
    
         chdir EXPR
                 Changes the working directory to EXPR, if possible.
                 If EXPR is omitted, changes to the directory
                 specified by `$ENV{HOME}', if set; if not, changes
                 to the directory specified by `$ENV{LOGDIR}'.  If
                 neither is set, `chdir' does nothing.  It returns
                 true upon success, false otherwise.  See the example
                 under `die'.
    
         chmod LIST
                 Changes the permissions of a list of files.  The
                 first element of the list must be the numerical
                 mode, which should probably be an octal number, and
                 which definitely should not a string of octal
                 digits:  `0644' is okay, `'0644'' is not.  Returns
                 the number of files successfully changed.  See also
                 the oct entry elsewhere in this document, if all you
                 have is a string.
    
    
    
                     $cnt = chmod 0755, 'foo', 'bar';
                     chmod 0755, @executables;
                     $mode = '0644'; chmod $mode, 'foo';      # !!! sets mode to
                                                              # --w----r-T
                     $mode = '0644'; chmod oct($mode), 'foo'; # this is better
                     $mode = 0644;   chmod $mode, 'foo';      # this is best
    
                 You can also import the symbolic `S_I*' constants
                 from the Fcntl module:
    
                     use Fcntl ':mode';
    
                     chmod S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH, @executables;
                     # This is identical to the chmod 0755 of the above example.
    
    
         chomp VARIABLE
    
         chomp LIST
    
         chomp   This safer version of the chop entry elsewhere in
                 this document removes any trailing string that
                 corresponds to the current value of `$/' (also known
                 as $INPUT_RECORD_SEPARATOR in the `English' module).
                 It returns the total number of characters removed
                 from all its arguments.  It's often used to remove
                 the newline from the end of an input record when
                 you're worried that the final record may be missing
                 its newline.  When in paragraph mode (`$/ = ""'), it
                 removes all trailing newlines from the string.  When
                 in slurp mode (`$/ = undef') or fixed-length record
                 mode (`$/' is a reference to an integer or the like,
                 see the perlvar manpage) chomp() won't remove
                 anything. If VARIABLE is omitted, it chomps `$_'.
                 Example:
    
                     while (<>) {
                         chomp;  # avoid \n on last field
                         @array = split(/:/);
                         # ...
                     }
    
                 You can actually chomp anything that's an lvalue,
                 including an assignment:
    
                     chomp($cwd = `pwd`);
                     chomp($answer = <STDIN>);
    
                 If you chomp a list, each element is chomped, and
                 the total number of characters removed is returned.
    
    
         chop VARIABLE
    
         chop LIST
    
         chop    Chops off the last character of a string and returns
                 the character chopped.  It's used primarily to
                 remove the newline from the end of an input record,
                 but is much more efficient than `s/\n//' because it
                 neither scans nor copies the string.  If VARIABLE is
                 omitted, chops `$_'.  Example:
    
                     while (<>) {
                         chop;   # avoid \n on last field
                         @array = split(/:/);
                         #...
                     }
    
                 You can actually chop anything that's an lvalue,
                 including an assignment:
    
                     chop($cwd = `pwd`);
                     chop($answer = <STDIN>);
    
                 If you chop a list, each element is chopped.  Only
                 the value of the last `chop' is returned.
    
                 Note that `chop' returns the last character.  To
                 return all but the last character, use
                 `substr($string, 0, -1)'.
    
         chown LIST
                 Changes the owner (and group) of a list of files.
                 The first two elements of the list must be the
                 numeric uid and gid, in that order.  A value of -1
                 in either position is interpreted by most systems to
                 leave that value unchanged.  Returns the number of
                 files successfully changed.
    
                     $cnt = chown $uid, $gid, 'foo', 'bar';
                     chown $uid, $gid, @filenames;
    
                 Here's an example that looks up nonnumeric uids in
                 the passwd file:
    
                     print "User: ";
                     chomp($user = <STDIN>);
                     print "Files: ";
                     chomp($pattern = <STDIN>);
    
                     ($login,$pass,$uid,$gid) = getpwnam($user)
                         or die "$user not in passwd file";
    
                     @ary = glob($pattern);      # expand filenames
                     chown $uid, $gid, @ary;
    
                 On most systems, you are not allowed to change the
                 ownership of the file unless you're the superuser,
                 although you should be able to change the group to
                 any of your secondary groups.  On insecure systems,
                 these restrictions may be relaxed, but this is not a
                 portable assumption.  On POSIX systems, you can
                 detect this condition this way:
    
                     use POSIX qw(sysconf _PC_CHOWN_RESTRICTED);
                     $can_chown_giveaway = not sysconf(_PC_CHOWN_RESTRICTED);
    
    
         chr NUMBER
    
         chr     Returns the character represented by that NUMBER in
                 the character set.  For example, `chr(65)' is `"A"'
                 in either ASCII or Unicode, and chr(0x263a) is a
                 Unicode smiley face (but only within the scope of a
                 `use utf8').  For the reverse, use the ord entry
                 elsewhere in this document. See the utf8 manpage for
                 more about Unicode.
    
                 If NUMBER is omitted, uses `$_'.
    
         chroot FILENAME
    
         chroot  This function works like the system call by the same
                 name: it makes the named directory the new root
                 directory for all further pathnames that begin with
                 a `/' by your process and all its children.  (It
                 doesn't change your current working directory, which
                 is unaffected.)  For security reasons, this call is
                 restricted to the superuser.  If FILENAME is
                 omitted, does a `chroot' to `$_'.
    
         close FILEHANDLE
    
         close   Closes the file or pipe associated with the file
                 handle, returning true only if stdio successfully
                 flushes buffers and closes the system file
                 descriptor.  Closes the currently selected
                 filehandle if the argument is omitted.
    
                 You don't have to close FILEHANDLE if you are
                 immediately going to do another `open' on it,
                 because `open' will close it for you.  (See `open'.)
                 However, an explicit `close' on an input file resets
                 the line counter (`$.'), while the implicit close
                 done by `open' does not.
                 If the file handle came from a piped open `close'
                 will additionally return false if one of the other
                 system calls involved fails or if the program exits
                 with non-zero status.  (If the only problem was that
                 the program exited non-zero `$!' will be set to
                 `0'.)  Closing a pipe also waits for the process
                 executing on the pipe to complete, in case you want
                 to look at the output of the pipe afterwards, and
                 implicitly puts the exit status value of that
                 command into `$?'.
    
                 Prematurely closing the read end of a pipe (i.e.
                 before the process writing to it at the other end
                 has closed it) will result in a SIGPIPE being
                 delivered to the writer.  If the other end can't
                 handle that, be sure to read all the data before
                 closing the pipe.
    
                 Example:
    
                     open(OUTPUT, '|sort >foo')  # pipe to sort
                         or die "Can't start sort: $!";
                     #...                        # print stuff to output
                     close OUTPUT                # wait for sort to finish
                         or warn $! ? "Error closing sort pipe: $!"
                                    : "Exit status $? from sort";
                     open(INPUT, 'foo')          # get sort's results
                         or die "Can't open 'foo' for input: $!";
    
                 FILEHANDLE may be an expression whose value can be
                 used as an indirect filehandle, usually the real
                 filehandle name.
    
         closedir DIRHANDLE
                 Closes a directory opened by `opendir' and returns
                 the success of that system call.
    
                 DIRHANDLE may be an expression whose value can be
                 used as an indirect dirhandle, usually the real
                 dirhandle name.
    
         connect SOCKET,NAME
                 Attempts to connect to a remote socket, just as the
                 connect system call does.  Returns true if it
                 succeeded, false otherwise.  NAME should be a packed
                 address of the appropriate type for the socket.  See
                 the examples in the Sockets: Client/Server
                 Communication entry in the perlipc manpage.
    
         continue BLOCK
                 Actually a flow control statement rather than a
                 function.  If there is a `continue' BLOCK attached
                 to a BLOCK (typically in a `while' or `foreach'), it
                 is always executed just before the conditional is
                 about to be evaluated again, just like the third
                 part of a `for' loop in C.  Thus it can be used to
                 increment a loop variable, even when the loop has
                 been continued via the `next' statement (which is
                 similar to the C `continue' statement).
    
                 `last', `next', or `redo' may appear within a
                 `continue' block.  `last' and `redo' will behave as
                 if they had been executed within the main block.  So
                 will `next', but since it will execute a `continue'
                 block, it may be more entertaining.
    
                     while (EXPR) {
                         ### redo always comes here
                         do_something;
                     } continue {
                         ### next always comes here
                         do_something_else;
                         # then back the top to re-check EXPR
                     }
                     ### last always comes here
    
                 Omitting the `continue' section is semantically
                 equivalent to using an empty one, logically enough.
                 In that case, `next' goes directly back to check the
                 condition at the top of the loop.
    
         cos EXPR
                 Returns the cosine of EXPR (expressed in radians).
                 If EXPR is omitted, takes cosine of `$_'.
    
                 For the inverse cosine operation, you may use the
                 `Math::Trig::acos()' function, or use this relation:
    
                     sub acos { atan2( sqrt(1 - $_[0] * $_[0]), $_[0] ) }
    
    
         crypt PLAINTEXT,SALT
                 Encrypts a string exactly like the crypt(3) function
                 in the C library (assuming that you actually have a
                 version there that has not been extirpated as a
                 potential munition).  This can prove useful for
                 checking the password file for lousy passwords,
                 amongst other things.  Only the guys wearing white
                 hats should do this.
    
                 Note that `crypt' is intended to be a one-way
                 function, much like breaking eggs to make an
                 omelette.  There is no (known) corresponding decrypt
                 function.  As a result, this function isn't all that
                 useful for cryptography.  (For that, see your nearby
                 CPAN mirror.)
    
                 When verifying an existing encrypted string you
                 should use the encrypted text as the salt (like
                 `crypt($plain, $crypted) eq $crypted').  This allows
                 your code to work with the standard `crypt' and with
                 more exotic implementations.  When choosing a new
                 salt create a random two character string whose
                 characters come from the set `[./0-9A-Za-z]' (like
                 `join '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand
                 64, rand 64]').
    
                 Here's an example that makes sure that whoever runs
                 this program knows their own password:
    
                     $pwd = (getpwuid($<))[1];
    
                     system "stty -echo";
                     print "Password: ";
                     chomp($word = <STDIN>);
                     print "\n";
                     system "stty echo";
    
                     if (crypt($word, $pwd) ne $pwd) {
                         die "Sorry...\n";
                     } else {
                         print "ok\n";
                     }
    
                 Of course, typing in your own password to whoever
                 asks you for it is unwise.
    
                 The the crypt manpage function is unsuitable for
                 encrypting large quantities of data, not least of
                 all because you can't get the information back.
                 Look at the by-module/Crypt and by-module/PGP
                 directories on your favorite CPAN mirror for a slew
                 of potentially useful modules.
    
         dbmclose HASH
                 [This function has been largely superseded by the
                 `untie' function.]
    
                 Breaks the binding between a DBM file and a hash.
    
         dbmopen HASH,DBNAME,MASK
                 [This function has been largely superseded by the
                 `tie' function.]
    
                 This binds a dbm(3), ndbm(3), sdbm(3), gdbm(3), or
                 Berkeley DB file to a hash.  HASH is the name of the
                 hash.  (Unlike normal `open', the first argument is
                 not a filehandle, even though it looks like one).
                 DBNAME is the name of the database (without the .dir
                 or .pag extension if any).  If the database does not
                 exist, it is created with protection specified by
                 MASK (as modified by the `umask').  If your system
                 supports only the older DBM functions, you may
                 perform only one `dbmopen' in your program.  In
                 older versions of Perl, if your system had neither
                 DBM nor ndbm, calling `dbmopen' produced a fatal
                 error; it now falls back to sdbm(3).
    
                 If you don't have write access to the DBM file, you
                 can only read hash variables, not set them.  If you
                 want to test whether you can write, either use file
                 tests or try setting a dummy hash entry inside an
                 `eval', which will trap the error.
    
                 Note that functions such as `keys' and `values' may
                 return huge lists when used on large DBM files.  You
                 may prefer to use the `each' function to iterate
                 over large DBM files.  Example:
    
                     # print out history file offsets
                     dbmopen(%HIST,'/usr/lib/news/history',0666);
                     while (($key,$val) = each %HIST) {
                         print $key, ' = ', unpack('L',$val), "\n";
                     }
                     dbmclose(%HIST);
    
                 See also the AnyDBM_File manpage for a more general
                 description of the pros and cons of the various dbm
                 approaches, as well as the DB_File manpage for a
                 particularly rich implementation.
    
                 You can control which DBM library you use by loading
                 that library before you call dbmopen():
    
                     use DB_File;
                     dbmopen(%NS_Hist, "$ENV{HOME}/.netscape/history.db")
                         or die "Can't open netscape history file: $!";
    
    
         defined EXPR
    
         defined Returns a Boolean value telling whether EXPR has a
                 value other than the undefined value `undef'.  If
                 EXPR is not present, `$_' will be checked.
    
                 Many operations return `undef' to indicate failure,
                 end of file, system error, uninitialized variable,
                 and other exceptional conditions.  This function
                 allows you to distinguish `undef' from other values.
                 (A simple Boolean test will not distinguish among
                 `undef', zero, the empty string, and `"0"', which
                 are all equally false.)  Note that since `undef' is
                 a valid scalar, its presence doesn't necessarily
                 indicate an exceptional condition: `pop' returns
                 `undef' when its argument is an empty array, or when
                 the element to return happens to be `undef'.
    
                 You may also use `defined(&func)' to check whether
                 subroutine `&func' has ever been defined.  The
                 return value is unaffected by any forward
                 declarations of `&foo'.
    
                 Use of `defined' on aggregates (hashes and arrays)
                 is deprecated.  It used to report whether memory for
                 that aggregate has ever been allocated.  This
                 behavior may disappear in future versions of Perl.
                 You should instead use a simple test for size:
    
                     if (@an_array) { print "has array elements\n" }
                     if (%a_hash)   { print "has hash members\n"   }
    
                 When used on a hash element, it tells you whether
                 the value is defined, not whether the key exists in
                 the hash.  Use the exists entry elsewhere in this
                 document for the latter purpose.
    
                 Examples:
    
                     print if defined $switch{'D'};
                     print "$val\n" while defined($val = pop(@ary));
                     die "Can't readlink $sym: $!"
                         unless defined($value = readlink $sym);
                     sub foo { defined &$bar ? &$bar(@_) : die "No bar"; }
                     $debugging = 0 unless defined $debugging;
    
                 Note:  Many folks tend to overuse `defined', and
                 then are surprised to discover that the number `0'
                 and `""' (the zero-length string) are, in fact,
                 defined values.  For example, if you say
    
                     "ab" =~ /a(.*)b/;
    
                 The pattern match succeeds, and `$1' is defined,
                 despite the fact that it matched "nothing".  But it
                 didn't really match nothing--rather, it matched
                 something that happened to be zero characters long.
                 This is all very above-board and honest.  When a
                 function returns an undefined value, it's an
                 admission that it couldn't give you an honest
                 answer.  So you should use `defined' only when
                 you're questioning the integrity of what you're
                 trying to do.  At other times, a simple comparison
                 to `0' or `""' is what you want.
    
                 See also the undef, exists, and ref entries
                 elsewhere in this document.
    
         delete EXPR
                 Given an expression that specifies a hash element,
                 array element, hash slice, or array slice, deletes
                 the specified element(s) from the hash or array.  In
                 the case of an array, if the array elements happen
                 to be at the end, the size of the array will shrink
                 to the highest element that tests true for exists()
                 (or 0 if no such element exists).
    
                 Returns each element so deleted or the undefined
                 value if there was no such element.  Deleting from
                 `$ENV{}' modifies the environment.  Deleting from a
                 hash tied to a DBM file deletes the entry from the
                 DBM file.  Deleting from a `tie'd hash or array may
                 not necessarily return anything.
    
                 Deleting an array element effectively returns that
                 position of the array to its initial, uninitialized
                 state.  Subsequently testing for the same element
                 with exists() will return false.  Note that deleting
                 array elements in the middle of an array will not
                 shift the index of the ones after them down--use
                 splice() for that.  See the exists entry elsewhere
                 in this document.
    
                 The following (inefficiently) deletes all the values
                 of %HASH and @ARRAY:
    
                     foreach $key (keys %HASH) {
                         delete $HASH{$key};
                     }
    
                     foreach $index (0 .. $#ARRAY) {
                         delete $ARRAY[$index];
                     }
    
                 And so do these:
    
                     delete @HASH{keys %HASH};
    
                     delete @ARRAY[0 .. $#ARRAY];
    
                 But both of these are slower than just assigning the
                 empty list or undefining %HASH or @ARRAY:
    
                     %HASH = ();         # completely empty %HASH
                     undef %HASH;        # forget %HASH ever existed
    
                     @ARRAY = ();        # completely empty @ARRAY
                     undef @ARRAY;       # forget @ARRAY ever existed
    
                 Note that the EXPR can be arbitrarily complicated as
                 long as the final operation is a hash element, array
                 element,  hash slice, or array slice lookup:
    
                     delete $ref->[$x][$y]{$key};
                     delete @{$ref->[$x][$y]}{$key1, $key2, @morekeys};
    
                     delete $ref->[$x][$y][$index];
                     delete @{$ref->[$x][$y]}[$index1, $index2, @moreindices];
    
    
         die LIST
                 Outside an `eval', prints the value of LIST to
                 `STDERR' and exits with the current value of `$!'
                 (errno).  If `$!' is `0', exits with the value of
                 `($? >> 8)' (backtick `command` status).  If `($? >>
                 8)' is `0', exits with `255'.  Inside an `eval(),'
                 the error message is stuffed into `$@' and the
                 `eval' is terminated with the undefined value.  This
                 makes `die' the way to raise an exception.
    
                 Equivalent examples:
    
                     die "Can't cd to spool: $!\n" unless chdir '/usr/spool/news';
                     chdir '/usr/spool/news' or die "Can't cd to spool: $!\n"
    
                 If the value of EXPR does not end in a newline, the
                 current script line number and input line number (if
                 any) are also printed, and a newline is supplied.
                 Note that the "input line number" (also known as
                 "chunk") is subject to whatever notion of "line"
                 happens to be currently in effect, and is also
                 available as the special variable `$.'.  See the
                 section on "$/" in the perlvar manpage and the
                 section on "$." in the perlvar manpage.
    
                 Hint: sometimes appending `", stopped"' to your
                 message will cause it to make better sense when the
                 string `"at foo line 123"' is appended.  Suppose you
                 are running script "canasta".
    
                     die "/etc/games is no good";
                     die "/etc/games is no good, stopped";
    
                 produce, respectively
    
                     /etc/games is no good at canasta line 123.
                     /etc/games is no good, stopped at canasta line 123.
    
                 See also exit(), warn(), and the Carp module.
    
                 If LIST is empty and `$@' already contains a value
                 (typically from a previous eval) that value is
                 reused after appending `"\t...propagated"'.  This is
                 useful for propagating exceptions:
    
                     eval { ... };
                     die unless $@ =~ /Expected exception/;
    
                 If `$@' is empty then the string `"Died"' is used.
    
                 die() can also be called with a reference argument.
                 If this happens to be trapped within an eval(), $@
                 contains the reference.  This behavior permits a
                 more elaborate exception handling implementation
                 using objects that maintain arbitary state about the
                 nature of the exception.  Such a scheme is sometimes
                 preferable to matching particular string values of
                 $@ using regular expressions.  Here's an example:
    
                     eval { ... ; die Some::Module::Exception->new( FOO => "bar" ) };
                     if ($@) {
                         if (ref($@) && UNIVERSAL::isa($@,"Some::Module::Exception")) {
                             # handle Some::Module::Exception
                         }
                         else {
                             # handle all other possible exceptions
                         }
                     }
    
                 Because perl will stringify uncaught exception
                 messages before displaying them, you may want to
                 overload stringification operations on such custom
                 exception objects.  See the overload manpage for
                 details about that.
    
                 You can arrange for a callback to be run just before
                 the `die' does its deed, by setting the
                 `$SIG{__DIE__}' hook.  The associated handler will
                 be called with the error text and can change the
                 error message, if it sees fit, by calling `die'
                 again.  See the section on "$SIG{expr}" in the
                 perlvar manpage for details on setting `%SIG'
                 entries, and the section on "eval BLOCK" for some
                 examples.  Although this feature was meant to be run
                 only right before your program was to exit, this is
                 not currently the case--the `$SIG{__DIE__}' hook is
                 currently called even inside eval()ed
                 blocks/strings!  If one wants the hook to do nothing
                 in such situations, put
    
                         die @_ if $^S;
    
                 as the first line of the handler (see the section on
                 "$^S" in the perlvar manpage).  Because this
                 promotes strange action at a distance, this
                 counterintuitive behavior may be fixed in a future
                 release.
    
         do BLOCK
                 Not really a function.  Returns the value of the
                 last command in the sequence of commands indicated
                 by BLOCK.  When modified by a loop modifier,
                 executes the BLOCK once before testing the loop
                 condition.  (On other statements the loop modifiers
                 test the conditional first.)
    
                 `do BLOCK' does not count as a loop, so the loop
                 control statements `next', `last', or `redo' cannot
                 be used to leave or restart the block.  See the
                 perlsyn manpage for alternative strategies.
    
         do SUBROUTINE(LIST)
                 A deprecated form of subroutine call.  See the
                 perlsub manpage.
    
         do EXPR Uses the value of EXPR as a filename and executes
                 the contents of the file as a Perl script.  Its
                 primary use is to include subroutines from a Perl
                 subroutine library.
    
                     do 'stat.pl';
    
                 is just like
    
                     scalar eval `cat stat.pl`;
    
                 except that it's more efficient and concise, keeps
                 track of the current filename for error messages,
                 searches the @INC libraries, and updates `%INC' if
                 the file is found.  See the Predefined Names entry
                 in the perlvar manpage for these variables.  It also
                 differs in that code evaluated with `do FILENAME'
                 cannot see lexicals in the enclosing scope; `eval
                 STRING' does.  It's the same, however, in that it
                 does reparse the file every time you call it, so you
                 probably don't want to do this inside a loop.
    
                 If `do' cannot read the file, it returns undef and
                 sets `$!' to the error.  If `do' can read the file
                 but cannot compile it, it returns undef and sets an
                 error message in `$@'.   If the file is successfully
                 compiled, `do' returns the value of the last
                 expression evaluated.
    
                 Note that inclusion of library modules is better
                 done with the `use' and `require' operators, which
                 also do automatic error checking and raise an
                 exception if there's a problem.
    
                 You might like to use `do' to read in a program
                 configuration file.  Manual error checking can be
                 done this way:
    
                     # read in config files: system first, then user
                     for $file ("/share/prog/defaults.rc",
                                "$ENV{HOME}/.someprogrc")
                    {
                         unless ($return = do $file) {
                             warn "couldn't parse $file: $@" if $@;
                             warn "couldn't do $file: $!"    unless defined $return;
                             warn "couldn't run $file"       unless $return;
                         }
                     }
    
    
         dump LABEL
    
         dump    This function causes an immediate core dump.  See
                 also the -u command-line switch in the perlrun
                 manpage, which does the same thing.  Primarily this
                 is so that you can use the undump program (not
                 supplied) to turn your core dump into an executable
                 binary after having initialized all your variables
                 at the beginning of the program.  When the new
                 binary is executed it will begin by executing a
                 `goto LABEL' (with all the restrictions that `goto'
                 suffers).  Think of it as a goto with an intervening
                 core dump and reincarnation.  If `LABEL' is omitted,
                 restarts the program from the top.
    
                 WARNING: Any files opened at the time of the dump
                 will not be open any more when the program is
                 reincarnated, with possible resulting confusion on
                 the part of Perl.
    
                 This function is now largely obsolete, partly
                 because it's very hard to convert a core file into
                 an executable, and because the real compiler
                 backends for generating portable bytecode and
                 compilable C code have superseded it.
    
                 If you're looking to use the dump manpage to speed
                 up your program, consider generating bytecode or
                 native C code as described in the perlcc manpage.
                 If you're just trying to accelerate a CGI script,
                 consider using the `mod_perl' extension to Apache,
                 or the CPAN module, Fast::CGI.  You might also
                 consider autoloading or selfloading, which at least
                 make your program appear to run faster.
    
         each HASH
                 When called in list context, returns a 2-element
                 list consisting of the key and value for the next
                 element of a hash, so that you can iterate over it.
                 When called in scalar context, returns the key for
                 only the "next" element in the hash.
    
                 Entries are returned in an apparently random order.
                 The actual random order is subject to change in
                 future versions of perl, but it is guaranteed to be
                 in the same order as either the `keys' or `values'
                 function would produce on the same (unmodified)
                 hash.
    
                 When the hash is entirely read, a null array is
                 returned in list context (which when assigned
                 produces a false (`0') value), and `undef' in scalar
                 context.  The next call to `each' after that will
                 start iterating again.  There is a single iterator
                 for each hash, shared by all `each', `keys', and
                 `values' function calls in the program; it can be
                 reset by reading all the elements from the hash, or
                 by evaluating `keys HASH' or `values HASH'.  If you
                 add or delete elements of a hash while you're
                 iterating over it, you may get entries skipped or
                 duplicated, so don't.
    
                 The following prints out your environment like the
                 printenv(1) program, only in a different order:
    
                     while (($key,$value) = each %ENV) {
                         print "$key=$value\n";
                     }
    
                 See also `keys', `values' and `sort'.
    
         eof FILEHANDLE
    
         eof ()
    
         eof     Returns 1 if the next read on FILEHANDLE will return
                 end of file, or if FILEHANDLE is not open.
                 FILEHANDLE may be an expression whose value gives
                 the real filehandle.  (Note that this function
                 actually reads a character and then `ungetc's it, so
                 isn't very useful in an interactive context.)  Do
                 not read from a terminal file (or call
                 `eof(FILEHANDLE)' on it) after end-of-file is
                 reached.  File types such as terminals may lose the
                 end-of-file condition if you do.
    
                 An `eof' without an argument uses the last file
                 read.  Using `eof()' with empty parentheses is very
                 different.  It refers to the pseudo file formed from
                 the files listed on the command line and accessed
                 via the `<>' operator.  Since `<>' isn't explicitly
                 opened, as a normal filehandle is, an `eof()' before
                 `<>' has been used will cause `@ARGV' to be examined
                 to determine if input is available.
    
                 In a `while (<>)' loop, `eof' or `eof(ARGV)' can be
                 used to detect the end of each file, `eof()' will
                 only detect the end of the last file.  Examples:
    
                     # reset line numbering on each input file
                     while (<>) {
                         next if /^\s*#/;        # skip comments
                         print "$.\t$_";
                     } continue {
                         close ARGV  if eof;     # Not eof()!
                     }
    
                     # insert dashes just before last line of last file
                     while (<>) {
                         if (eof()) {            # check for end of current file
                             print "--------------\n";
                             close(ARGV);        # close or last; is needed if we
                                                 # are reading from the terminal
                         }
                         print;
                     }
    
                 Practical hint: you almost never need to use `eof'
                 in Perl, because the input operators typically
                 return `undef' when they run out of data, or if
                 there was an error.
    
         eval EXPR
    
         eval BLOCK
                 In the first form, the return value of EXPR is
                 parsed and executed as if it were a little Perl
                 program.  The value of the expression (which is
                 itself determined within scalar context) is first
                 parsed, and if there weren't any errors, executed in
                 the context of the current Perl program, so that any
                 variable settings or subroutine and format
                 definitions remain afterwards.  Note that the value
                 is parsed every time the eval executes.  If EXPR is
                 omitted, evaluates `$_'.  This form is typically
                 used to delay parsing and subsequent execution of
                 the text of EXPR until run time.
    
                 In the second form, the code within the BLOCK is
                 parsed only once--at the same time the code
                 surrounding the eval itself was parsed--and executed
                 within the context of the current Perl program.
                 This form is typically used to trap exceptions more
                 efficiently than the first (see below), while also
                 providing the benefit of checking the code within
                 BLOCK at compile time.
    
                 The final semicolon, if any, may be omitted from the
                 value of EXPR or within the BLOCK.
    
                 In both forms, the value returned is the value of
                 the last expression evaluated inside the mini-
                 program; a return statement may be also used, just
                 as with subroutines.  The expression providing the
                 return value is evaluated in void, scalar, or list
                 context, depending on the context of the eval
                 itself.  See the wantarray entry elsewhere in this
                 document for more on how the evaluation context can
                 be determined.
    
                 If there is a syntax error or runtime error, or a
                 `die' statement is executed, an undefined value is
                 returned by `eval', and `$@' is set to the error
                 message.  If there was no error, `$@' is guaranteed
                 to be a null string.  Beware that using `eval'
                 neither silences perl from printing warnings to
                 STDERR, nor does it stuff the text of warning
                 messages into `$@'.  To do either of those, you have
                 to use the `$SIG{__WARN__}' facility.  See the warn
                 entry elsewhere in this document and the perlvar
                 manpage.
    
                 Note that, because `eval' traps otherwise-fatal
                 errors, it is useful for determining whether a
                 particular feature (such as `socket' or `symlink')
                 is implemented.  It is also Perl's exception
                 trapping mechanism, where the die operator is used
                 to raise exceptions.
    
                 If the code to be executed doesn't vary, you may use
                 the eval-BLOCK form to trap run-time errors without
                 incurring the penalty of recompiling each time.  The
                 error, if any, is still returned in `$@'.  Examples:
    
                     # make divide-by-zero nonfatal
                     eval { $answer = $a / $b; }; warn $@ if $@;
    
                     # same thing, but less efficient
                     eval '$answer = $a / $b'; warn $@ if $@;
    
                     # a compile-time error
                     eval { $answer = };                 # WRONG
    
                     # a run-time error
                     eval '$answer =';   # sets $@
    
                 Due to the current arguably broken state of
                 `__DIE__' hooks, when using the `eval{}' form as an
                 exception trap in libraries, you may wish not to
                 trigger any `__DIE__' hooks that user code may have
                 installed.  You can use the `local $SIG{__DIE__}'
                 construct for this purpose, as shown in this
                 example:
    
                     # a very private exception trap for divide-by-zero
                     eval { local $SIG{'__DIE__'}; $answer = $a / $b; };
                     warn $@ if $@;
    
                 This is especially significant, given that `__DIE__'
                 hooks can call `die' again, which has the effect of
                 changing their error messages:
    
                     # __DIE__ hooks may modify error messages
                     {
                        local $SIG{'__DIE__'} =
                               sub { (my $x = $_[0]) =~ s/foo/bar/g; die $x };
                        eval { die "foo lives here" };
                        print $@ if $@;                # prints "bar lives here"
                     }
    
                 Because this promotes action at a distance, this
                 counterintuitive behavior may be fixed in a future
                 release.
    
                 With an `eval', you should be especially careful to
                 remember what's being looked at when:
    
                     eval $x;            # CASE 1
                     eval "$x";          # CASE 2
    
                     eval '$x';          # CASE 3
                     eval { $x };        # CASE 4
    
    
                     eval "\$$x++";      # CASE 5
                     $$x++;              # CASE 6
    
                 Cases 1 and 2 above behave identically: they run the
                 code contained in the variable $x.  (Although case 2
                 has misleading double quotes making the reader
                 wonder what else might be happening (nothing is).)
                 Cases 3 and 4 likewise behave in the same way: they
                 run the code `'$x'', which does nothing but return
                 the value of $x.  (Case 4 is preferred for purely
                 visual reasons, but it also has the advantage of
                 compiling at compile-time instead of at run-time.)
                 Case 5 is a place where normally you would like to
                 use double quotes, except that in this particular
                 situation, you can just use symbolic references
                 instead, as in case 6.
    
                 `eval BLOCK' does not count as a loop, so the loop
                 control statements `next', `last', or `redo' cannot
                 be used to leave or restart the block.
    
         exec LIST
    
         exec PROGRAM LIST
                 The `exec' function executes a system command and
                 never returns-- use `system' instead of `exec' if
                 you want it to return.  It fails and returns false
                 only if the command does not exist and it is
                 executed directly instead of via your system's
                 command shell (see below).
    
                 Since it's a common mistake to use `exec' instead of
                 `system', Perl warns you if there is a following
                 statement which isn't `die', `warn', or `exit' (if
                 `-w' is set  -  but you always do that).   If you
                 really want to follow an `exec' with some other
                 statement, you can use one of these styles to avoid
                 the warning:
    
                     exec ('foo')   or print STDERR "couldn't exec foo: $!";
                     { exec ('foo') }; print STDERR "couldn't exec foo: $!";
    
                 If there is more than one argument in LIST, or if
                 LIST is an array with more than one value, calls
                 execvp(3) with the arguments in LIST.  If there is
                 only one scalar argument or an array with one
                 element in it, the argument is checked for shell
                 metacharacters, and if there are any, the entire
                 argument is passed to the system's command shell for
                 parsing (this is `/bin/sh -c' on Unix platforms, but
                 varies on other platforms).  If there are no shell
                 metacharacters in the argument, it is split into
                 words and passed directly to `execvp', which is more
                 efficient. Examples:
    
                     exec '/bin/echo', 'Your arguments are: ', @ARGV;
                     exec "sort $outfile | uniq";
    
                 If you don't really want to execute the first
                 argument, but want to lie to the program you are
                 executing about its own name, you can specify the
                 program you actually want to run as an "indirect
                 object" (without a comma) in front of the LIST.
                 (This always forces interpretation of the LIST as a
                 multivalued list, even if there is only a single
                 scalar in the list.)  Example:
    
                     $shell = '/bin/csh';
                     exec $shell '-sh';          # pretend it's a login shell
    
                 or, more directly,
    
                     exec {'/bin/csh'} '-sh';    # pretend it's a login shell
    
                 When the arguments get executed via the system
                 shell, results will be subject to its quirks and
                 capabilities.  See the section on "`STRING`" in the
                 perlop manpage for details.
    
                 Using an indirect object with `exec' or `system' is
                 also more secure.  This usage (which also works fine
                 with system()) forces interpretation of the
                 arguments as a multivalued list, even if the list
                 had just one argument.  That way you're safe from
                 the shell expanding wildcards or splitting up words
                 with whitespace in them.
    
                     @args = ( "echo surprise" );
    
                     exec @args;               # subject to shell escapes
                                                 # if @args == 1
                     exec { $args[0] } @args;  # safe even with one-arg list
    
                 The first version, the one without the indirect
                 object, ran the echo program, passing it
                 `"surprise"' an argument.  The second version
                 didn't--it tried to run a program literally called
                 "echo surprise", didn't find it, and set `$?' to a
                 non-zero value indicating failure.
    
                 Beginning with v5.6.0, Perl will attempt to flush
                 all files opened for output before the exec, but
                 this may not be supported on some platforms (see the
                 perlport manpage).  To be safe, you may need to set
                 `$|' ($AUTOFLUSH in English) or call the
                 `autoflush()' method of `IO::Handle' on any open
                 handles in order to avoid lost output.
    
                 Note that `exec' will not call your `END' blocks,
                 nor will it call any `DESTROY' methods in your
                 objects.
    
         exists EXPR
                 Given an expression that specifies a hash element or
                 array element, returns true if the specified element
                 in the hash or array has ever been initialized, even
                 if the corresponding value is undefined.  The
                 element is not autovivified if it doesn't exist.
    
                     print "Exists\n"    if exists $hash{$key};
                     print "Defined\n"   if defined $hash{$key};
                     print "True\n"      if $hash{$key};
    
                     print "Exists\n"    if exists $array[$index];
                     print "Defined\n"   if defined $array[$index];
                     print "True\n"      if $array[$index];
    
                 A hash or array element can be true only if it's
                 defined, and defined if it exists, but the reverse
                 doesn't necessarily hold true.
    
                 Given an expression that specifies the name of a
                 subroutine, returns true if the specified subroutine
                 has ever been declared, even if it is undefined.
                 Mentioning a subroutine name for exists or defined
                 does not count as declaring it.
    
                     print "Exists\n"    if exists &subroutine;
                     print "Defined\n"   if defined &subroutine;
    
                 Note that the EXPR can be arbitrarily complicated as
                 long as the final operation is a hash or array key
                 lookup or subroutine name:
    
                     if (exists $ref->{A}->{B}->{$key})  { }
                     if (exists $hash{A}{B}{$key})       { }
    
                     if (exists $ref->{A}->{B}->[$ix])   { }
                     if (exists $hash{A}{B}[$ix])        { }
    
                     if (exists &{$ref->{A}{B}{$key}})   { }
    
                 Although the deepest nested array or hash will not
                 spring into existence just because its existence was
                 tested, any intervening ones will.  Thus
                 `$ref->{"A"}' and `$ref->{"A"}->{"B"}' will spring
                 into existence due to the existence test for the
                 $key element above.  This happens anywhere the arrow
                 operator is used, including even:
    
                     undef $ref;
                     if (exists $ref->{"Some key"})      { }
                     print $ref;             # prints HASH(0x80d3d5c)
    
                 This surprising autovivification in what does not at
                 first--or even second--glance appear to be an lvalue
                 context may be fixed in a future release.
    
                 See the Pseudo-hashes: Using an array as a hash
                 entry in the perlref manpage for specifics on how
                 exists() acts when used on a pseudo-hash.
    
                 Use of a subroutine call, rather than a subroutine
                 name, as an argument to exists() is an error.
    
                     exists &sub;        # OK
                     exists &sub();      # Error
    
    
         exit EXPR
                 Evaluates EXPR and exits immediately with that
                 value.    Example:
    
                     $ans = <STDIN>;
                     exit 0 if $ans =~ /^[Xx]/;
    
                 See also `die'.  If EXPR is omitted, exits with `0'
                 status.  The only universally recognized values for
                 EXPR are `0' for success and `1' for error; other
                 values are subject to interpretation depending on
                 the environment in which the Perl program is
                 running.  For example, exiting 69 (EX_UNAVAILABLE)
                 from a sendmail incoming-mail filter will cause the
                 mailer to return the item undelivered, but that's
                 not true everywhere.
    
                 Don't use `exit' to abort a subroutine if there's
                 any chance that someone might want to trap whatever
                 error happened.  Use `die' instead, which can be
                 trapped by an `eval'.
    
                 The exit() function does not always exit
                 immediately.  It calls any defined `END' routines
                 first, but these `END' routines may not themselves
                 abort the exit.  Likewise any object destructors
                 that need to be called are called before the real
                 exit.  If this is a problem, you can call
                 `POSIX:_exit($status)' to avoid END and destructor
                 processing.  See the perlmod manpage for details.
    
         exp EXPR
    
         exp     Returns e (the natural logarithm base) to the power
                 of EXPR. If EXPR is omitted, gives `exp($_)'.
    
         fcntl FILEHANDLE,FUNCTION,SCALAR
                 Implements the fcntl(2) function.  You'll probably
                 have to say
    
                     use Fcntl;
    
                 first to get the correct constant definitions.
                 Argument processing and value return works just like
                 `ioctl' below. For example:
    
                     use Fcntl;
                     fcntl($filehandle, F_GETFL, $packed_return_buffer)
                         or die "can't fcntl F_GETFL: $!";
    
                 You don't have to check for `defined' on the return
                 from `fnctl'.  Like `ioctl', it maps a `0' return
                 from the system call into `"0 but true"' in Perl.
                 This string is true in boolean context and `0' in
                 numeric context.  It is also exempt from the normal
                 -w warnings on improper numeric conversions.
    
                 Note that `fcntl' will produce a fatal error if used
                 on a machine that doesn't implement fcntl(2).  See
                 the Fcntl module or your fcntl(2) manpage to learn
                 what functions are available on your system.
    
         fileno FILEHANDLE
                 Returns the file descriptor for a filehandle, or
                 undefined if the filehandle is not open.  This is
                 mainly useful for constructing bitmaps for `select'
                 and low-level POSIX tty-handling operations.  If
                 FILEHANDLE is an expression, the value is taken as
                 an indirect filehandle, generally its name.
    
                 You can use this to find out whether two handles
                 refer to the same underlying descriptor:
    
                     if (fileno(THIS) == fileno(THAT)) {
                         print "THIS and THAT are dups\n";
                     }
    
    
         flock FILEHANDLE,OPERATION
                 Calls flock(2), or an emulation of it, on
                 FILEHANDLE.  Returns true for success, false on
                 failure.  Produces a fatal error if used on a
                 machine that doesn't implement flock(2), fcntl(2)
                 locking, or lockf(3).  `flock' is Perl's portable
                 file locking interface, although it locks only
                 entire files, not records.
    
                 Two potentially non-obvious but traditional `flock'
                 semantics are that it waits indefinitely until the
                 lock is granted, and that its locks merely advisory.
                 Such discretionary locks are more flexible, but
                 offer fewer guarantees.  This means that files
                 locked with `flock' may be modified by programs that
                 do not also use `flock'.  See the perlport manpage,
                 your port's specific documentation, or your system-
                 specific local manpages for details.  It's best to
                 assume traditional behavior if you're writing
                 portable programs.  (But if you're not, you should
                 as always feel perfectly free to write for your own
                 system's idiosyncrasies (sometimes called
                 "features").  Slavish adherence to portability
                 concerns shouldn't get in the way of your getting
                 your job done.)
    
                 OPERATION is one of LOCK_SH, LOCK_EX, or LOCK_UN,
                 possibly combined with LOCK_NB.  These constants are
                 traditionally valued 1, 2, 8 and 4, but you can use
                 the symbolic names if you import them from the Fcntl
                 module, either individually, or as a group using the
                 ':flock' tag.  LOCK_SH requests a shared lock,
                 LOCK_EX requests an exclusive lock, and LOCK_UN
                 releases a previously requested lock.  If LOCK_NB is
                 bitwise-or'ed with LOCK_SH or LOCK_EX then `flock'
                 will return immediately rather than blocking waiting
                 for the lock (check the return status to see if you
                 got it).
    
                 To avoid the possibility of miscoordination, Perl
                 now flushes FILEHANDLE before locking or unlocking
                 it.
    
                 Note that the emulation built with lockf(3) doesn't
                 provide shared locks, and it requires that
                 FILEHANDLE be open with write intent.  These are the
                 semantics that lockf(3) implements.  Most if not all
                 systems implement lockf(3) in terms of fcntl(2)
                 locking, though, so the differing semantics
                 shouldn't bite too many people.
    
                 Note also that some versions of `flock' cannot lock
                 things over the network; you would need to use the
                 more system-specific `fcntl' for that.  If you like
                 you can force Perl to ignore your system's flock(2)
                 function, and so provide its own fcntl(2)-based
                 emulation, by passing the switch `-Ud_flock' to the
                 Configure program when you configure perl.
    
                 Here's a mailbox appender for BSD systems.
    
                     use Fcntl ':flock'; # import LOCK_* constants
    
                     sub lock {
                         flock(MBOX,LOCK_EX);
                         # and, in case someone appended
                         # while we were waiting...
                         seek(MBOX, 0, 2);
                     }
    
                     sub unlock {
                         flock(MBOX,LOCK_UN);
                     }
    
                     open(MBOX, ">>/usr/spool/mail/$ENV{'USER'}")
                             or die "Can't open mailbox: $!";
    
                     lock();
                     print MBOX $msg,"\n\n";
                     unlock();
    
                 On systems that support a real flock(), locks are
                 inherited across fork() calls, whereas those that
                 must resort to the more capricious fcntl() function
                 lose the locks, making it harder to write servers.
    
                 See also the DB_File manpage for other flock()
                 examples.
    
         fork    Does a fork(2) system call to create a new process
                 running the same program at the same point.  It
                 returns the child pid to the parent process, `0' to
                 the child process, or `undef' if the fork is
                 unsuccessful.  File descriptors (and sometimes locks
                 on those descriptors) are shared, while everything
                 else is copied.  On most systems supporting fork(),
                 great care has gone into making it extremely
                 efficient (for example, using copy-on-write
                 technology on data pages), making it the dominant
                 paradigm for multitasking over the last few decades.
    
                 Beginning with v5.6.0, Perl will attempt to flush
                 all files opened for output before forking the child
                 process, but this may not be supported on some
                 platforms (see the perlport manpage).  To be safe,
                 you may need to set `$|' ($AUTOFLUSH in English) or
                 call the `autoflush()' method of `IO::Handle' on any
                 open handles in order to avoid duplicate output.
    
                 If you `fork' without ever waiting on your children,
                 you will accumulate zombies.  On some systems, you
                 can avoid this by setting `$SIG{CHLD}' to
                 `"IGNORE"'.  See also the perlipc manpage for more
                 examples of forking and reaping moribund children.
    
                 Note that if your forked child inherits system file
                 descriptors like STDIN and STDOUT that are actually
                 connected by a pipe or socket, even if you exit,
                 then the remote server (such as, say, a CGI script
                 or a backgrounded job launched from a remote shell)
                 won't think you're done.  You should reopen those to
                 /dev/null if it's any issue.
    
         format  Declare a picture format for use by the `write'
                 function.  For example:
    
                     format Something =
                         Test: @<<<<<<<< @||||| @>>>>>
                               $str,     $%,    '$' . int($num)
                     .
    
                     $str = "widget";
                     $num = $cost/$quantity;
                     $~ = 'Something';
                     write;
    
                 See the perlform manpage for many details and
                 examples.
    
         formline PICTURE,LIST
                 This is an internal function used by `format's,
                 though you may call it, too.  It formats (see the
                 perlform manpage) a list of values according to the
                 contents of PICTURE, placing the output into the
                 format output accumulator, `$^A' (or `$ACCUMULATOR'
                 in English).  Eventually, when a `write' is done,
                 the contents of `$^A' are written to some
                 filehandle, but you could also read `$^A' yourself
                 and then set `$^A' back to `""'.  Note that a format
                 typically does one `formline' per line of form, but
                 the `formline' function itself doesn't care how many
                 newlines are embedded in the PICTURE.  This means
                 that the `~' and `~~' tokens will treat the entire
                 PICTURE as a single line.  You may therefore need to
                 use multiple formlines to implement a single record
                 format, just like the format compiler.
    
                 Be careful if you put double quotes around the
                 picture, because an `@' character may be taken to
                 mean the beginning of an array name.  `formline'
                 always returns true.  See the perlform manpage for
                 other examples.
    
         getc FILEHANDLE
    
         getc    Returns the next character from the input file
                 attached to FILEHANDLE, or the undefined value at
                 end of file, or if there was an error.  If
                 FILEHANDLE is omitted, reads from STDIN.  This is
                 not particularly efficient.  However, it cannot be
                 used by itself to fetch single characters without
                 waiting for the user to hit enter.  For that, try
                 something more like:
    
                     if ($BSD_STYLE) {
                         system "stty cbreak </dev/tty >/dev/tty 2>&1";
                     }
                     else {
                         system "stty", '-icanon', 'eol', "\001";
                     }
    
                     $key = getc(STDIN);
    
                     if ($BSD_STYLE) {
                         system "stty -cbreak </dev/tty >/dev/tty 2>&1";
                     }
                     else {
                         system "stty", 'icanon', 'eol', '^@'; # ASCII null
                     }
                     print "\n";
    
                 Determination of whether $BSD_STYLE should be set is
                 left as an exercise to the reader.
    
                 The `POSIX::getattr' function can do this more
                 portably on systems purporting POSIX compliance.
                 See also the `Term::ReadKey' module from your
                 nearest CPAN site; details on CPAN can be found on
                 the CPAN entry in the perlmodlib manpage.
    
         getlogin
                 Implements the C library function of the same name,
                 which on most systems returns the current login from
                 /etc/utmp, if any.  If null, use `getpwuid'.
    
                     $login = getlogin || getpwuid($<) || "Kilroy";
    
                 Do not consider `getlogin' for authentication: it is
                 not as secure as `getpwuid'.
    
    
         getpeername SOCKET
                 Returns the packed sockaddr address of other end of
                 the SOCKET connection.
    
                     use Socket;
                     $hersockaddr    = getpeername(SOCK);
                     ($port, $iaddr) = sockaddr_in($hersockaddr);
                     $herhostname    = gethostbyaddr($iaddr, AF_INET);
                     $herstraddr     = inet_ntoa($iaddr);
    
    
         getpgrp PID
                 Returns the current process group for the specified
                 PID.  Use a PID of `0' to get the current process
                 group for the current process.  Will raise an
                 exception if used on a machine that doesn't
                 implement getpgrp(2).  If PID is omitted, returns
                 process group of current process.  Note that the
                 POSIX version of `getpgrp' does not accept a PID
                 argument, so only `PID==0' is truly portable.
    
         getppid Returns the process id of the parent process.
    
         getpriority WHICH,WHO
                 Returns the current priority for a process, a
                 process group, or a user.  (See getpriority(2).)
                 Will raise a fatal exception if used on a machine
                 that doesn't implement getpriority(2).
    
         getpwnam NAME
    
         getgrnam NAME
    
         gethostbyname NAME
    
         getnetbyname NAME
    
         getprotobyname NAME
    
         getpwuid UID
    
         getgrgid GID
    
         getservbyname NAME,PROTO
    
         gethostbyaddr ADDR,ADDRTYPE
    
         getnetbyaddr ADDR,ADDRTYPE
    
         getprotobynumber NUMBER
    
    
         getservbyport PORT,PROTO
    
         getpwent
    
         getgrent
    
         gethostent
    
         getnetent
    
         getprotoent
    
         getservent
    
         setpwent
    
         setgrent
    
         sethostent STAYOPEN
    
         setnetent STAYOPEN
    
         setprotoent STAYOPEN
    
         setservent STAYOPEN
    
         endpwent
    
         endgrent
    
         endhostent
    
         endnetent
    
         endprotoent
    
         endservent
                 These routines perform the same functions as their
                 counterparts in the system library.  In list
                 context, the return values from the various get
                 routines are as follows:
    
                     ($name,$passwd,$uid,$gid,
                        $quota,$comment,$gcos,$dir,$shell,$expire) = getpw*
                     ($name,$passwd,$gid,$members) = getgr*
                     ($name,$aliases,$addrtype,$length,@addrs) = gethost*
                     ($name,$aliases,$addrtype,$net) = getnet*
                     ($name,$aliases,$proto) = getproto*
                     ($name,$aliases,$port,$proto) = getserv*
    
                 (If the entry doesn't exist you get a null list.)
    
                 The exact meaning of the $gcos field varies but it
                 usually contains the real name of the user (as
                 opposed to the login name) and other information
                 pertaining to the user.  Beware, however, that in
                 many system users are able to change this
                 information and therefore it cannot be trusted and
                 therefore the $gcos is is tainted (see the perlsec
                 manpage).  The $passwd and $shell, user's encrypted
                 password and login shell, are also tainted, because
                 of the same reason.
    
                 In scalar context, you get the name, unless the
                 function was a lookup by name, in which case you get
                 the other thing, whatever it is.  (If the entry
                 doesn't exist you get the undefined value.)  For
                 example:
    
                     $uid   = getpwnam($name);
                     $name  = getpwuid($num);
                     $name  = getpwent();
                     $gid   = getgrnam($name);
                     $name  = getgrgid($num;
                     $name  = getgrent();
                     #etc.
    
                 In getpw*() the fields $quota, $comment, and $expire
                 are special cases in the sense that in many systems
                 they are unsupported.  If the $quota is unsupported,
                 it is an empty scalar.  If it is supported, it
                 usually encodes the disk quota.  If the $comment
                 field is unsupported, it is an empty scalar.  If it
                 is supported it usually encodes some administrative
                 comment about the user.  In some systems the $quota
                 field may be $change or $age, fields that have to do
                 with password aging.  In some systems the $comment
                 field may be $class.  The $expire field, if present,
                 encodes the expiration period of the account or the
                 password.  For the availability and the exact
                 meaning of these fields in your system, please
                 consult your getpwnam(3) documentation and your
                 pwd.h file.  You can also find out from within Perl
                 what your $quota and $comment fields mean and
                 whether you have the $expire field by using the
                 `Config' module and the values `d_pwquota',
                 `d_pwage', `d_pwchange', `d_pwcomment', and
                 `d_pwexpire'.  Shadow password files are only
                 supported if your vendor has implemented them in the
                 intuitive fashion that calling the regular C library
                 routines gets the shadow versions if you're running
                 under privilege.  Those that incorrectly implement a
                 separate library call are not supported.
    
                 The $members value returned by getgr*() is a space
                 separated list of the login names of the members of
                 the group.
    
                 For the gethost*() functions, if the `h_errno'
                 variable is supported in C, it will be returned to
                 you via `$?' if the function call fails.  The
                 `@addrs' value returned by a successful call is a
                 list of the raw addresses returned by the
                 corresponding system library call.  In the Internet
                 domain, each address is four bytes long and you can
                 unpack it by saying something like:
    
                     ($a,$b,$c,$d) = unpack('C4',$addr[0]);
    
                 The Socket library makes this slightly easier:
    
                     use Socket;
                     $iaddr = inet_aton("127.1"); # or whatever address
                     $name  = gethostbyaddr($iaddr, AF_INET);
    
                     # or going the other way
                     $straddr = inet_ntoa($iaddr);
    
                 If you get tired of remembering which element of the
                 return list contains which return value, by-name
                 interfaces are provided in standard modules:
                 `File::stat', `Net::hostent', `Net::netent',
                 `Net::protoent', `Net::servent', `Time::gmtime',
                 `Time::localtime', and `User::grent'.  These
                 override the normal built-ins, supplying versions
                 that return objects with the appropriate names for
                 each field.  For example:
    
                    use File::stat;
                    use User::pwent;
                    $is_his = (stat($filename)->uid == pwent($whoever)->uid);
    
                 Even though it looks like they're the same method
                 calls (uid), they aren't, because a `File::stat'
                 object is different from a `User::pwent' object.
    
         getsockname SOCKET
                 Returns the packed sockaddr address of this end of
                 the SOCKET connection, in case you don't know the
                 address because you have several different IPs that
                 the connection might have come in on.
    
    
    
                     use Socket;
                     $mysockaddr = getsockname(SOCK);
                     ($port, $myaddr) = sockaddr_in($mysockaddr);
                     printf "Connect to %s [%s]\n",
                        scalar gethostbyaddr($myaddr, AF_INET),
                        inet_ntoa($myaddr);
    
    
         getsockopt SOCKET,LEVEL,OPTNAME
                 Returns the socket option requested, or undef if
                 there is an error.
    
         glob EXPR
    
         glob    Returns the value of EXPR with filename expansions
                 such as the standard Unix shell /bin/csh would do.
                 This is the internal function implementing the
                 `<*.c>' operator, but you can use it directly.  If
                 EXPR is omitted, `$_' is used.  The `<*.c>' operator
                 is discussed in more detail in the I/O Operators
                 entry in the perlop manpage.
    
                 Beginning with v5.6.0, this operator is implemented
                 using the standard `File::Glob' extension.  See the
                 File::Glob manpage for details.
    
         gmtime EXPR
                 Converts a time as returned by the time function to
                 a 8-element list with the time localized for the
                 standard Greenwich time zone.  Typically used as
                 follows:
    
                     #  0    1    2     3     4    5     6     7
                     ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday) =
                                                             gmtime(time);
    
                 All list elements are numeric, and come straight out
                 of the C `struct tm'.  $sec, $min, and $hour are the
                 seconds, minutes, and hours of the specified time.
                 $mday is the day of the month, and $mon is the month
                 itself, in the range `0..11' with 0 indicating
                 January and 11 indicating December.  $year is the
                 number of years since 1900.  That is, $year is `123'
                 in year 2023.  $wday is the day of the week, with 0
                 indicating Sunday and 3 indicating Wednesday.  $yday
                 is the day of the year, in the range `1..365' (or
                 `1..366' in leap years.)
    
                 Note that the $year element is not simply the last
                 two digits of the year.  If you assume it is, then
                 you create non-Y2K-compliant programs--and you
                 wouldn't want to do that, would you?
                 The proper way to get a complete 4-digit year is
                 simply:
    
                         $year += 1900;
    
                 And to get the last two digits of the year (e.g.,
                 '01' in 2001) do:
    
                         $year = sprintf("%02d", $year % 100);
    
                 If EXPR is omitted, `gmtime()' uses the current time
                 (`gmtime(time)').
    
                 In scalar context, `gmtime()' returns the ctime(3)
                 value:
    
                     $now_string = gmtime;  # e.g., "Thu Oct 13 04:54:34 1994"
    
                 Also see the `timegm' function provided by the
                 `Time::Local' module, and the strftime(3) function
                 available via the POSIX module.
    
                 This scalar value is not locale dependent (see the
                 perllocale manpage), but is instead a Perl builtin.
                 Also see the `Time::Local' module, and the
                 strftime(3) and mktime(3) functions available via
                 the POSIX module.  To get somewhat similar but
                 locale dependent date strings, set up your locale
                 environment variables appropriately (please see the
                 perllocale manpage) and try for example:
    
                     use POSIX qw(strftime);
                     $now_string = strftime "%a %b %e %H:%M:%S %Y", gmtime;
    
                 Note that the `%a' and `%b' escapes, which represent
                 the short forms of the day of the week and the month
                 of the year, may not necessarily be three characters
                 wide in all locales.
    
         goto LABEL
    
         goto EXPR
    
         goto &NAME
                 The `goto-LABEL' form finds the statement labeled
                 with LABEL and resumes execution there.  It may not
                 be used to go into any construct that requires
                 initialization, such as a subroutine or a `foreach'
                 loop.  It also can't be used to go into a construct
                 that is optimized away, or to get out of a block or
                 subroutine given to `sort'.  It can be used to go
                 almost anywhere else within the dynamic scope,
                 including out of subroutines, but it's usually
                 better to use some other construct such as `last' or
                 `die'.  The author of Perl has never felt the need
                 to use this form of `goto' (in Perl, that is--C is
                 another matter).
    
                 The `goto-EXPR' form expects a label name, whose
                 scope will be resolved dynamically.  This allows for
                 computed `goto's per FORTRAN, but isn't necessarily
                 recommended if you're optimizing for
                 maintainability:
    
                     goto ("FOO", "BAR", "GLARCH")[$i];
    
                 The `goto-&NAME' form is quite different from the
                 other forms of `goto'.  In fact, it isn't a goto in
                 the normal sense at all, and doesn't have the stigma
                 associated with other gotos.  Instead, it
                 substitutes a call to the named subroutine for the
                 currently running subroutine.  This is used by
                 `AUTOLOAD' subroutines that wish to load another
                 subroutine and then pretend that the other
                 subroutine had been called in the first place
                 (except that any modifications to `@_' in the
                 current subroutine are propagated to the other
                 subroutine.)  After the `goto', not even `caller'
                 will be able to tell that this routine was called
                 first.
    
                 NAME needn't be the name of a subroutine; it can be
                 a scalar variable containing a code reference, or a
                 block which evaluates to a code reference.
    
         grep BLOCK LIST
    
         grep EXPR,LIST
                 This is similar in spirit to, but not the same as,
                 grep(1) and its relatives.  In particular, it is not
                 limited to using regular expressions.
    
                 Evaluates the BLOCK or EXPR for each element of LIST
                 (locally setting `$_' to each element) and returns
                 the list value consisting of those elements for
                 which the expression evaluated to true.  In scalar
                 context, returns the number of times the expression
                 was true.
    
                     @foo = grep(!/^#/, @bar);    # weed out comments
    
                 or equivalently,
    
                     @foo = grep {!/^#/} @bar;    # weed out comments
    
                 Note that, because `$_' is a reference into the list
                 value, it can be used to modify the elements of the
                 array.  While this is useful and supported, it can
                 cause bizarre results if the LIST is not a named
                 array.  Similarly, grep returns aliases into the
                 original list, much as a for loop's index variable
                 aliases the list elements.  That is, modifying an
                 element of a list returned by grep (for example, in
                 a `foreach', `map' or another `grep') actually
                 modifies the element in the original list.  This is
                 usually something to be avoided when writing clear
                 code.
    
                 See also the map entry elsewhere in this document
                 for a list composed of the results of the BLOCK or
                 EXPR.
    
         hex EXPR
    
         hex     Interprets EXPR as a hex string and returns the
                 corresponding value.  (To convert strings that might
                 start with either 0, 0x, or 0b, see the oct entry
                 elsewhere in this document.)  If EXPR is omitted,
                 uses `$_'.
    
                     print hex '0xAf'; # prints '175'
                     print hex 'aF';   # same
    
                 Hex strings may only represent integers.  Strings
                 that would cause integer overflow trigger a warning.
    
         import  There is no builtin `import' function.  It is just
                 an ordinary method (subroutine) defined (or
                 inherited) by modules that wish to export names to
                 another module.  The `use' function calls the
                 `import' method for the package used.  See also the
                 use() entry elsewhere in this document, the perlmod
                 manpage, and the Exporter manpage.
    
         index STR,SUBSTR,POSITION
    
         index STR,SUBSTR
                 The index function searches for one string within
                 another, but without the wildcard-like behavior of a
                 full regular-expression pattern match.  It returns
                 the position of the first occurrence of SUBSTR in
                 STR at or after POSITION.  If POSITION is omitted,
                 starts searching from the beginning of the string.
                 The return value is based at `0' (or whatever you've
                 set the `$[' variable to--but don't do that).  If
                 the substring is not found, returns one less than
                 the base, ordinarily `-1'.
    
         int EXPR
    
         int     Returns the integer portion of EXPR.  If EXPR is
                 omitted, uses `$_'.  You should not use this
                 function for rounding: one because it truncates
                 towards `0', and two because machine representations
                 of floating point numbers can sometimes produce
                 counterintuitive results.  For example,
                 `int(-6.725/0.025)' produces -268 rather than the
                 correct -269; that's because it's really more like
                 -268.99999999999994315658 instead.  Usually, the
                 `sprintf', `printf', or the `POSIX::floor' and
                 `POSIX::ceil' functions will serve you better than
                 will int().
    
         ioctl FILEHANDLE,FUNCTION,SCALAR
                 Implements the ioctl(2) function.  You'll probably
                 first have to say
    
                     require "ioctl.ph"; # probably in /usr/local/lib/perl/ioctl.ph
    
                 to get the correct function definitions.  If
                 ioctl.ph doesn't exist or doesn't have the correct
                 definitions you'll have to roll your own, based on
                 your C header files such as <sys/ioctl.h>.  (There
                 is a Perl script called h2ph that comes with the
                 Perl kit that may help you in this, but it's
                 nontrivial.)  SCALAR will be read and/or written
                 depending on the FUNCTION--a pointer to the string
                 value of SCALAR will be passed as the third argument
                 of the actual `ioctl' call.  (If SCALAR has no
                 string value but does have a numeric value, that
                 value will be passed rather than a pointer to the
                 string value.  To guarantee this to be true, add a
                 `0' to the scalar before using it.)  The `pack' and
                 `unpack' functions may be needed to manipulate the
                 values of structures used by `ioctl'.
    
                 The return value of `ioctl' (and `fcntl') is as
                 follows:
    
                         if OS returns:          then Perl returns:
                             -1                    undefined value
                              0                  string "0 but true"
                         anything else               that number
    
                 Thus Perl returns true on success and false on
                 failure, yet you can still easily determine the
                 actual value returned by the operating system:
    
                     $retval = ioctl(...) || -1;
                     printf "System returned %d\n", $retval;
    
                 The special string "`0' but true" is exempt from -w
                 complaints about improper numeric conversions.
    
                 Here's an example of setting a filehandle named
                 `REMOTE' to be non-blocking at the system level.
                 You'll have to negotiate `$|' on your own, though.
    
                     use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK);
    
                     $flags = fcntl(REMOTE, F_GETFL, 0)
                                 or die "Can't get flags for the socket: $!\n";
    
                     $flags = fcntl(REMOTE, F_SETFL, $flags | O_NONBLOCK)
                                 or die "Can't set flags for the socket: $!\n";
    
    
         join EXPR,LIST
                 Joins the separate strings of LIST into a single
                 string with fields separated by the value of EXPR,
                 and returns that new string.  Example:
    
                     $rec = join(':', $login,$passwd,$uid,$gid,$gcos,$home,$shell);
    
                 Beware that unlike `split', `join' doesn't take a
                 pattern as its first argument.  Compare the split
                 entry elsewhere in this document.
    
         keys HASH
                 Returns a list consisting of all the keys of the
                 named hash.  (In scalar context, returns the number
                 of keys.)  The keys are returned in an apparently
                 random order.  The actual random order is subject to
                 change in future versions of perl, but it is
                 guaranteed to be the same order as either the
                 `values' or `each' function produces (given that the
                 hash has not been modified).  As a side effect, it
                 resets HASH's iterator.
    
                 Here is yet another way to print your environment:
    
                     @keys = keys %ENV;
                     @values = values %ENV;
                     while (@keys) {
                         print pop(@keys), '=', pop(@values), "\n";
                     }
    
                 or how about sorted by key:
    
                     foreach $key (sort(keys %ENV)) {
                         print $key, '=', $ENV{$key}, "\n";
                     }
    
                 To sort a hash by value, you'll need to use a `sort'
                 function.  Here's a descending numeric sort of a
                 hash by its values:
    
                     foreach $key (sort { $hash{$b} <=> $hash{$a} } keys %hash) {
                         printf "%4d %s\n", $hash{$key}, $key;
                     }
    
                 As an lvalue `keys' allows you to increase the
                 number of hash buckets allocated for the given hash.
                 This can gain you a measure of efficiency if you
                 know the hash is going to get big.  (This is similar
                 to pre-extending an array by assigning a larger
                 number to $#array.)  If you say
    
                     keys %hash = 200;
    
                 then `%hash' will have at least 200 buckets
                 allocated for it--256 of them, in fact, since it
                 rounds up to the next power of two.  These buckets
                 will be retained even if you do `%hash = ()', use
                 `undef %hash' if you want to free the storage while
                 `%hash' is still in scope.  You can't shrink the
                 number of buckets allocated for the hash using
                 `keys' in this way (but you needn't worry about
                 doing this by accident, as trying has no effect).
    
                 See also `each', `values' and `sort'.
    
         kill SIGNAL, LIST
                 Sends a signal to a list of processes.  Returns the
                 number of processes successfully signaled (which is
                 not necessarily the same as the number actually
                 killed).
    
                     $cnt = kill 1, $child1, $child2;
                     kill 9, @goners;
    
                 If SIGNAL is zero, no signal is sent to the process.
                 This is a useful way to check that the process is
                 alive and hasn't changed its UID.  See the perlport
                 manpage for notes on the portability of this
                 construct.
    
                 Unlike in the shell, if SIGNAL is negative, it kills
                 process groups instead of processes.  (On System V,
                 a negative PROCESS number will also kill process
                 groups, but that's not portable.)  That means you
                 usually want to use positive not negative signals.
                 You may also use a signal name in quotes.  See the
                 Signals entry in the perlipc manpage for details.
    
         last LABEL
    
         last    The `last' command is like the `break' statement in
                 C (as used in loops); it immediately exits the loop
                 in question.  If the LABEL is omitted, the command
                 refers to the innermost enclosing loop.  The
                 `continue' block, if any, is not executed:
    
                     LINE: while (<STDIN>) {
                         last LINE if /^$/;      # exit when done with header
                         #...
                     }
    
                 `last' cannot be used to exit a block which returns
                 a value such as `eval {}', `sub {}' or `do {}', and
                 should not be used to exit a grep() or map()
                 operation.
    
                 Note that a block by itself is semantically
                 identical to a loop that executes once.  Thus `last'
                 can be used to effect an early exit out of such a
                 block.
    
                 See also the continue entry elsewhere in this
                 document for an illustration of how `last', `next',
                 and `redo' work.
    
         lc EXPR
    
         lc      Returns an lowercased version of EXPR.  This is the
                 internal function implementing the `\L' escape in
                 double-quoted strings.  Respects current LC_CTYPE
                 locale if `use locale' in force.  See the perllocale
                 manpage and the utf8 manpage.
    
                 If EXPR is omitted, uses `$_'.
    
         lcfirst EXPR
    
         lcfirst Returns the value of EXPR with the first character
                 lowercased.  This is the internal function
                 implementing the `\l' escape in double-quoted
                 strings.  Respects current LC_CTYPE locale if `use
                 locale' in force.  See the perllocale manpage.
    
                 If EXPR is omitted, uses `$_'.
    
         length EXPR
    
         length  Returns the length in characters of the value of
                 EXPR.  If EXPR is omitted, returns length of `$_'.
                 Note that this cannot be used on an entire array or
                 hash to find out how many elements these have.  For
                 that, use `scalar @array' and `scalar keys %hash'
                 respectively.
    
         link OLDFILE,NEWFILE
                 Creates a new filename linked to the old filename.
                 Returns true for success, false otherwise.
    
         listen SOCKET,QUEUESIZE
                 Does the same thing that the listen system call
                 does.  Returns true if it succeeded, false
                 otherwise.  See the example in the Sockets:
                 Client/Server Communication entry in the perlipc
                 manpage.
    
         local EXPR
                 You really probably want to be using `my' instead,
                 because `local' isn't what most people think of as
                 "local".  See the Private Variables via my() entry
                 in the perlsub manpage for details.
    
                 A local modifies the listed variables to be local to
                 the enclosing block, file, or eval.  If more than
                 one value is listed, the list must be placed in
                 parentheses.  See the Temporary Values via local()
                 entry in the perlsub manpage for details, including
                 issues with tied arrays and hashes.
    
         localtime EXPR
                 Converts a time as returned by the time function to
                 a 9-element list with the time analyzed for the
                 local time zone.  Typically used as follows:
    
                     #  0    1    2     3     4    5     6     7     8
                     ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
                                                                 localtime(time);
    
                 All list elements are numeric, and come straight out
                 of the C `struct tm'.  $sec, $min, and $hour are the
                 seconds, minutes, and hours of the specified time.
                 $mday is the day of the month, and $mon is the month
                 itself, in the range `0..11' with 0 indicating
                 January and 11 indicating December.  $year is the
                 number of years since 1900.  That is, $year is `123'
                 in year 2023.  $wday is the day of the week, with 0
                 indicating Sunday and 3 indicating Wednesday.  $yday
                 is the day of the year, in the range `1..365' (or
                 `1..366' in leap years.)  $isdst is true if the
                 specified time occurs during daylight savings time,
                 false otherwise.
    
                 Note that the $year element is not simply the last
                 two digits of the year.  If you assume it is, then
                 you create non-Y2K-compliant programs--and you
                 wouldn't want to do that, would you?
    
                 The proper way to get a complete 4-digit year is
                 simply:
    
                         $year += 1900;
    
                 And to get the last two digits of the year (e.g.,
                 '01' in 2001) do:
    
                         $year = sprintf("%02d", $year % 100);
    
                 If EXPR is omitted, `localtime()' uses the current
                 time (`localtime(time)').
    
                 In scalar context, `localtime()' returns the
                 ctime(3) value:
    
                     $now_string = localtime;  # e.g., "Thu Oct 13 04:54:34 1994"
    
                 This scalar value is not locale dependent, see the
                 perllocale manpage, but instead a Perl builtin.
                 Also see the `Time::Local' module (to convert the
                 second, minutes, hours, ... back to seconds since
                 the stroke of midnight the 1st of January 1970, the
                 value returned by time()), and the strftime(3) and
                 mktime(3) functions available via the POSIX module.
                 To get somewhat similar but locale dependent date
                 strings, set up your locale environment variables
                 appropriately (please see the perllocale manpage)
                 and try for example:
    
                     use POSIX qw(strftime);
                     $now_string = strftime "%a %b %e %H:%M:%S %Y", localtime;
    
                 Note that the `%a' and `%b', the short forms of the
                 day of the week and the month of the year, may not
                 necessarily be three characters wide.
    
         lock
                     lock I<THING>
    
                 This function places an advisory lock on a variable,
                 subroutine, or referenced object contained in THING
                 until the lock goes out of scope.  This is a built-
                 in function only if your version of Perl was built
                 with threading enabled, and if you've said `use
                 Threads'.  Otherwise a user-defined function by this
                 name will be called.  See the Thread manpage.
    
         log EXPR
    
         log     Returns the natural logarithm (base e) of EXPR.  If
                 EXPR is omitted, returns log of `$_'.  To get the
                 log of another base, use basic algebra:  The base-N
                 log of a number is equal to the natural log of that
                 number divided by the natural log of N.  For
                 example:
    
                     sub log10 {
                         my $n = shift;
                         return log($n)/log(10);
                     }
    
                 See also the exp entry elsewhere in this document
                 for the inverse operation.
    
         lstat FILEHANDLE
    
         lstat EXPR
    
         lstat   Does the same thing as the `stat' function
                 (including setting the special `_' filehandle) but
                 stats a symbolic link instead of the file the
                 symbolic link points to.  If symbolic links are
                 unimplemented on your system, a normal `stat' is
                 done.
    
                 If EXPR is omitted, stats `$_'.
    
         m//     The match operator.  See the perlop manpage.
    
         map BLOCK LIST
    
         map EXPR,LIST
                 Evaluates the BLOCK or EXPR for each element of LIST
                 (locally setting `$_' to each element) and returns
                 the list value composed of the results of each such
                 evaluation.  In scalar context, returns the total
                 number of elements so generated.  Evaluates BLOCK or
                 EXPR in list context, so each element of LIST may
                 produce zero, one, or more elements in the returned
                 value.
    
                     @chars = map(chr, @nums);
    
                 translates a list of numbers to the corresponding
                 characters.  And
    
                     %hash = map { getkey($_) => $_ } @array;
    
                 is just a funny way to write
                     %hash = ();
                     foreach $_ (@array) {
                         $hash{getkey($_)} = $_;
                     }
    
                 Note that, because `$_' is a reference into the list
                 value, it can be used to modify the elements of the
                 array.  While this is useful and supported, it can
                 cause bizarre results if the LIST is not a named
                 array.  Using a regular `foreach' loop for this
                 purpose would be clearer in most cases.  See also
                 the grep entry elsewhere in this document for an
                 array composed of those items of the original list
                 for which the BLOCK or EXPR evaluates to true.
    
         mkdir FILENAME,MASK
    
         mkdir FILENAME
                 Creates the directory specified by FILENAME, with
                 permissions specified by MASK (as modified by
                 `umask').  If it succeeds it returns true, otherwise
                 it returns false and sets `$!' (errno).  If omitted,
                 MASK defaults to 0777.
    
                 In general, it is better to create directories with
                 permissive MASK, and let the user modify that with
                 their `umask', than it is to supply a restrictive
                 MASK and give the user no way to be more permissive.
                 The exceptions to this rule are when the file or
                 directory should be kept private (mail files, for
                 instance).  The perlfunc(1) entry on `umask'
                 discusses the choice of MASK in more detail.
    
         msgctl ID,CMD,ARG
                 Calls the System V IPC function msgctl(2).  You'll
                 probably have to say
    
                     use IPC::SysV;
    
                 first to get the correct constant definitions.  If
                 CMD is `IPC_STAT', then ARG must be a variable which
                 will hold the returned `msqid_ds' structure.
                 Returns like `ioctl': the undefined value for error,
                 `"0 but true"' for zero, or the actual return value
                 otherwise.  See also `IPC::SysV' and
                 `IPC::Semaphore' documentation.
    
         msgget KEY,FLAGS
                 Calls the System V IPC function msgget(2).  Returns
                 the message queue id, or the undefined value if
                 there is an error.  See also `IPC::SysV' and
                 `IPC::Msg' documentation.
    
         msgrcv ID,VAR,SIZE,TYPE,FLAGS
                 Calls the System V IPC function msgrcv to receive a
                 message from message queue ID into variable VAR with
                 a maximum message size of SIZE.  Note that when a
                 message is received, the message type as a native
                 long integer will be the first thing in VAR,
                 followed by the actual message.  This packing may be
                 opened with `unpack("l! a*")'.  Taints the variable.
                 Returns true if successful, or false if there is an
                 error.  See also `IPC::SysV' and `IPC::SysV::Msg'
                 documentation.
    
         msgsnd ID,MSG,FLAGS
                 Calls the System V IPC function msgsnd to send the
                 message MSG to the message queue ID.  MSG must begin
                 with the native long integer message type, and be
                 followed by the length of the actual message, and
                 finally the message itself.  This kind of packing
                 can be achieved with `pack("l! a*", $type,
                 $message)'.  Returns true if successful, or false if
                 there is an error.  See also `IPC::SysV' and
                 `IPC::SysV::Msg' documentation.
    
         my EXPR
    
         my EXPR : ATTRIBUTES
                 A `my' declares the listed variables to be local
                 (lexically) to the enclosing block, file, or `eval'.
                 If more than one value is listed, the list must be
                 placed in parentheses.  See the Private Variables
                 via my() entry in the perlsub manpage for details.
    
         next LABEL
    
         next    The `next' command is like the `continue' statement
                 in C; it starts the next iteration of the loop:
    
                     LINE: while (<STDIN>) {
                         next LINE if /^#/;      # discard comments
                         #...
                     }
    
                 Note that if there were a `continue' block on the
                 above, it would get executed even on discarded
                 lines.  If the LABEL is omitted, the command refers
                 to the innermost enclosing loop.
    
                 `next' cannot be used to exit a block which returns
                 a value such as `eval {}', `sub {}' or `do {}', and
                 should not be used to exit a grep() or map()
                 operation.
    
                 Note that a block by itself is semantically
                 identical to a loop that executes once.  Thus `next'
                 will exit such a block early.
    
                 See also the continue entry elsewhere in this
                 document for an illustration of how `last', `next',
                 and `redo' work.
    
         no Module LIST
                 See the the use entry elsewhere in this document
                 function, which `no' is the opposite of.
    
         oct EXPR
    
         oct     Interprets EXPR as an octal string and returns the
                 corresponding value.  (If EXPR happens to start off
                 with `0x', interprets it as a hex string.  If EXPR
                 starts off with `0b', it is interpreted as a binary
                 string.)  The following will handle decimal, binary,
                 octal, and hex in the standard Perl or C notation:
    
                     $val = oct($val) if $val =~ /^0/;
    
                 If EXPR is omitted, uses `$_'.   To go the other way
                 (produce a number in octal), use sprintf() or
                 printf():
    
                     $perms = (stat("filename"))[2] & 07777;
                     $oct_perms = sprintf "%lo", $perms;
    
                 The oct() function is commonly used when a string
                 such as `644' needs to be converted into a file
                 mode, for example. (Although perl will automatically
                 convert strings into numbers as needed, this
                 automatic conversion assumes base 10.)
    
         open FILEHANDLE,MODE,LIST
    
         open FILEHANDLE,EXPR
    
         open FILEHANDLE
                 Opens the file whose filename is given by EXPR, and
                 associates it with FILEHANDLE.  If FILEHANDLE is an
                 expression, its value is used as the name of the
                 real filehandle wanted.  (This is considered a
                 symbolic reference, so `use strict 'refs'' should
                 not be in effect.)
    
                 If EXPR is omitted, the scalar variable of the same
                 name as the FILEHANDLE contains the filename.  (Note
                 that lexical variables--those declared with `my'--
                 will not work for this purpose; so if you're using
                 `my', specify EXPR in your call to open.)  See the
                 perlopentut manpage for a kinder, gentler
                 explanation of opening files.
    
                 If MODE is `'<'' or nothing, the file is opened for
                 input.  If MODE is `'>'', the file is truncated and
                 opened for output, being created if necessary.  If
                 MODE is `'>>'', the file is opened for appending,
                 again being created if necessary. You can put a
                 `'+'' in front of the `'>'' or `'<'' to indicate
                 that you want both read and write access to the
                 file; thus `'+<'' is almost always preferred for
                 read/write updates--the `'+>'' mode would clobber
                 the file first.  You can't usually use either read-
                 write mode for updating textfiles, since they have
                 variable length records.  See the -i switch in the
                 perlrun manpage for a better approach.  The file is
                 created with permissions of `0666' modified by the
                 process' `umask' value.
    
                 These various prefixes correspond to the fopen(3)
                 modes of `'r'', `'r+'', `'w'', `'w+'', `'a'', and
                 `'a+''.
    
                 In the 2-arguments (and 1-argument) form of the call
                 the mode and filename should be concatenated (in
                 this order), possibly separated by spaces.  It is
                 possible to omit the mode if the mode is `'<''.
    
                 If the filename begins with `'|'', the filename is
                 interpreted as a command to which output is to be
                 piped, and if the filename ends with a `'|'', the
                 filename is interpreted as a command which pipes
                 output to us.  See the Using open() for IPC entry in
                 the perlipc manpage for more examples of this.  (You
                 are not allowed to `open' to a command that pipes
                 both in and out, but see the IPC::Open2 manpage, the
                 IPC::Open3 manpage, and the Bidirectional
                 Communication with Another Process entry in the
                 perlipc manpage for alternatives.)
    
                 If MODE is `'|-'', the filename is interpreted as a
                 command to which output is to be piped, and if MODE
                 is `'-|'', the filename is interpreted as a command
                 which pipes output to us.  In the 2-arguments (and
                 1-argument) form one should replace dash (`'-'')
                 with the command.  See the Using open() for IPC
                 entry in the perlipc manpage for more examples of
                 this.  (You are not allowed to `open' to a command
                 that pipes both in and out, but see the IPC::Open2
                 manpage, the IPC::Open3 manpage, and the
                 Bidirectional Communication entry in the perlipc
                 manpage for alternatives.)
    
                 In the 2-arguments (and 1-argument) form opening
                 `'-'' opens STDIN and opening `'>-'' opens STDOUT.
    
                 Open returns nonzero upon success, the undefined
                 value otherwise.  If the `open' involved a pipe, the
                 return value happens to be the pid of the
                 subprocess.
    
                 If you're unfortunate enough to be running Perl on a
                 system that distinguishes between text files and
                 binary files (modern operating systems don't care),
                 then you should check out the binmode entry
                 elsewhere in this document for tips for dealing with
                 this.  The key distinction between systems that need
                 `binmode' and those that don't is their text file
                 formats.  Systems like Unix, MacOS, and Plan9, which
                 delimit lines with a single character, and which
                 encode that character in C as `"\n"', do not need
                 `binmode'.  The rest need it.
    
                 When opening a file, it's usually a bad idea to
                 continue normal execution if the request failed, so
                 `open' is frequently used in connection with `die'.
                 Even if `die' won't do what you want (say, in a CGI
                 script, where you want to make a nicely formatted
                 error message (but there are modules that can help
                 with that problem)) you should always check the
                 return value from opening a file.  The infrequent
                 exception is when working with an unopened
                 filehandle is actually what you want to do.
    
                 Examples:
    
                     $ARTICLE = 100;
                     open ARTICLE or die "Can't find article $ARTICLE: $!\n";
                     while (<ARTICLE>) {...
    
                     open(LOG, '>>/usr/spool/news/twitlog');     # (log is reserved)
                     # if the open fails, output is discarded
    
                     open(DBASE, '+<', 'dbase.mine')             # open for update
                         or die "Can't open 'dbase.mine' for update: $!";
    
                     open(DBASE, '+<dbase.mine')                 # ditto
                         or die "Can't open 'dbase.mine' for update: $!";
    
                     open(ARTICLE, '-|', "caesar <$article")     # decrypt article
                         or die "Can't start caesar: $!";
    
    
                     open(ARTICLE, "caesar <$article |")         # ditto
                         or die "Can't start caesar: $!";
    
                     open(EXTRACT, "|sort >/tmp/Tmp$$")          # $$ is our process id
                         or die "Can't start sort: $!";
    
                     # process argument list of files along with any includes
    
                     foreach $file (@ARGV) {
                         process($file, 'fh00');
                     }
    
                     sub process {
                         my($filename, $input) = @_;
                         $input++;               # this is a string increment
                         unless (open($input, $filename)) {
                             print STDERR "Can't open $filename: $!\n";
                             return;
                         }
    
                         local $_;
                         while (<$input>) {              # note use of indirection
                             if (/^#include "(.*)"/) {
                                 process($1, $input);
                                 next;
                             }
                             #...                # whatever
                         }
                     }
    
                 You may also, in the Bourne shell tradition, specify
                 an EXPR beginning with `'>&'', in which case the
                 rest of the string is interpreted as the name of a
                 filehandle (or file descriptor, if numeric) to be
                 duped and opened.  You may use `&' after `>', `>>',
                 `<', `+>', `+>>', and `+<'.  The mode you specify
                 should match the mode of the original filehandle.
                 (Duping a filehandle does not take into account any
                 existing contents of stdio buffers.)  Duping file
                 handles is not yet supported for 3-argument open().
    
                 Here is a script that saves, redirects, and restores
                 STDOUT and STDERR:
    
                     #!/usr/bin/perl
                     open(OLDOUT, ">&STDOUT");
                     open(OLDERR, ">&STDERR");
    
                     open(STDOUT, '>', "foo.out") || die "Can't redirect stdout";
                     open(STDERR, ">&STDOUT")     || die "Can't dup stdout";
    
    
                     select(STDERR); $| = 1;     # make unbuffered
                     select(STDOUT); $| = 1;     # make unbuffered
    
                     print STDOUT "stdout 1\n";  # this works for
                     print STDERR "stderr 1\n";  # subprocesses too
    
                     close(STDOUT);
                     close(STDERR);
    
                     open(STDOUT, ">&OLDOUT");
                     open(STDERR, ">&OLDERR");
    
                     print STDOUT "stdout 2\n";
                     print STDERR "stderr 2\n";
    
                 If you specify `'<&=N'', where `N' is a number, then
                 Perl will do an equivalent of C's `fdopen' of that
                 file descriptor; this is more parsimonious of file
                 descriptors.  For example:
    
                     open(FILEHANDLE, "<&=$fd")
    
                 Note that this feature depends on the fdopen() C
                 library function.  On many UNIX systems, fdopen() is
                 known to fail when file descriptors exceed a certain
                 value, typically 255. If you need more file
                 descriptors than that, consider rebuilding Perl to
                 use the `sfio' library.
    
                 If you open a pipe on the command `'-'', i.e.,
                 either `'|-'' or `'-|'' with 2-arguments (or
                 1-argument) form of open(), then there is an
                 implicit fork done, and the return value of open is
                 the pid of the child within the parent process, and
                 `0' within the child process.  (Use `defined($pid)'
                 to determine whether the open was successful.)  The
                 filehandle behaves normally for the parent, but i/o
                 to that filehandle is piped from/to the STDOUT/STDIN
                 of the child process.  In the child process the
                 filehandle isn't opened--i/o happens from/to the new
                 STDOUT or STDIN.  Typically this is used like the
                 normal piped open when you want to exercise more
                 control over just how the pipe command gets
                 executed, such as when you are running setuid, and
                 don't want to have to scan shell commands for
                 metacharacters.  The following triples are more or
                 less equivalent:
    
                     open(FOO, "|tr '[a-z]' '[A-Z]'");
                     open(FOO, '|-', "tr '[a-z]' '[A-Z]'");
                     open(FOO, '|-') || exec 'tr', '[a-z]', '[A-Z]';
    
                     open(FOO, "cat -n '$file'|");
                     open(FOO, '-|', "cat -n '$file'");
                     open(FOO, '-|') || exec 'cat', '-n', $file;
    
                 See the Safe Pipe Opens entry in the perlipc manpage
                 for more examples of this.
    
                 Beginning with v5.6.0, Perl will attempt to flush
                 all files opened for output before any operation
                 that may do a fork, but this may not be supported on
                 some platforms (see the perlport manpage).  To be
                 safe, you may need to set `$|' ($AUTOFLUSH in
                 English) or call the `autoflush()' method of
                 `IO::Handle' on any open handles.
    
                 On systems that support a close-on-exec flag on
                 files, the flag will be set for the newly opened
                 file descriptor as determined by the value of $^F.
                 See the section on "$^F" in the perlvar manpage.
    
                 Closing any piped filehandle causes the parent
                 process to wait for the child to finish, and returns
                 the status value in `$?'.
    
                 The filename passed to 2-argument (or 1-argument)
                 form of open() will have leading and trailing
                 whitespace deleted, and the normal redirection
                 characters honored.  This property, known as "magic
                 open", can often be used to good effect.  A user
                 could specify a filename of "rsh cat file |", or you
                 could change certain filenames as needed:
    
                     $filename =~ s/(.*\.gz)\s*$/gzip -dc < $1|/;
                     open(FH, $filename) or die "Can't open $filename: $!";
    
                 Use 3-argument form to open a file with arbitrary
                 weird characters in it,
    
                     open(FOO, '<', $file);
    
                 otherwise it's necessary to protect any leading and
                 trailing whitespace:
    
                     $file =~ s#^(\s)#./$1#;
                     open(FOO, "< $file\0");
    
                 (this may not work on some bizzare filesystems).
                 One should conscientiously choose between the the
                 magic and 3-arguments form of open():
    
                     open IN, $ARGV[0];
    
                 will allow the user to specify an argument of the
                 form `"rsh cat file |"', but will not work on a
                 filename which happens to have a trailing space,
                 while
    
                     open IN, '<', $ARGV[0];
    
                 will have exactly the opposite restrictions.
    
                 If you want a "real" C `open' (see open(2) on your
                 system), then you should use the `sysopen' function,
                 which involves no such magic (but may use subtly
                 different filemodes than Perl open(), which is
                 mapped to C fopen()).  This is another way to
                 protect your filenames from interpretation.  For
                 example:
    
                     use IO::Handle;
                     sysopen(HANDLE, $path, O_RDWR|O_CREAT|O_EXCL)
                         or die "sysopen $path: $!";
                     $oldfh = select(HANDLE); $| = 1; select($oldfh);
                     print HANDLE "stuff $$\n");
                     seek(HANDLE, 0, 0);
                     print "File contains: ", <HANDLE>;
    
                 Using the constructor from the `IO::Handle' package
                 (or one of its subclasses, such as `IO::File' or
                 `IO::Socket'), you can generate anonymous
                 filehandles that have the scope of whatever
                 variables hold references to them, and automatically
                 close whenever and however you leave that scope:
    
                     use IO::File;
                     #...
                     sub read_myfile_munged {
                         my $ALL = shift;
                         my $handle = new IO::File;
                         open($handle, "myfile") or die "myfile: $!";
                         $first = <$handle>
                             or return ();     # Automatically closed here.
                         mung $first or die "mung failed";       # Or here.
                         return $first, <$handle> if $ALL;       # Or here.
                         $first;                                 # Or here.
                     }
    
                 See the seek entry elsewhere in this document for
                 some details about mixing reading and writing.
    
         opendir DIRHANDLE,EXPR
                 Opens a directory named EXPR for processing by
                 `readdir', `telldir', `seekdir', `rewinddir', and
                 `closedir'.  Returns true if successful.  DIRHANDLEs
                 have their own namespace separate from FILEHANDLEs.
    
         ord EXPR
    
         ord     Returns the numeric (ASCII or Unicode) value of the
                 first character of EXPR.  If EXPR is omitted, uses
                 `$_'.  For the reverse, see the chr entry elsewhere
                 in this document.  See the utf8 manpage for more
                 about Unicode.
    
         our EXPR
                 An `our' declares the listed variables to be valid
                 globals within the enclosing block, file, or `eval'.
                 That is, it has the same scoping rules as a "my"
                 declaration, but does not create a local variable.
                 If more than one value is listed, the list must be
                 placed in parentheses.  The `our' declaration has no
                 semantic effect unless "use strict vars" is in
                 effect, in which case it lets you use the declared
                 global variable without qualifying it with a package
                 name.  (But only within the lexical scope of the
                 `our' declaration.  In this it differs from "use
                 vars", which is package scoped.)
    
                 An `our' declaration declares a global variable that
                 will be visible across its entire lexical scope,
                 even across package boundaries.  The package in
                 which the variable is entered is determined at the
                 point of the declaration, not at the point of use.
                 This means the following behavior holds:
    
                     package Foo;
                     our $bar;           # declares $Foo::bar for rest of lexical scope
                     $bar = 20;
    
                     package Bar;
                     print $bar;         # prints 20
    
                 Multiple `our' declarations in the same lexical
                 scope are allowed if they are in different packages.
                 If they happened to be in the same package, Perl
                 will emit warnings if you have asked for them.
    
                     use warnings;
                     package Foo;
                     our $bar;           # declares $Foo::bar for rest of lexical scope
                     $bar = 20;
    
                     package Bar;
                     our $bar = 30;      # declares $Bar::bar for rest of lexical scope
                     print $bar;         # prints 30
    
                     our $bar;           # emits warning
    
    
         pack TEMPLATE,LIST
                 Takes a LIST of values and converts it into a string
                 using the rules given by the TEMPLATE.  The
                 resulting string is the concatenation of the
                 converted values.  Typically, each converted value
                 looks like its machine-level representation.  For
                 example, on 32-bit machines a converted integer may
                 be represented by a sequence of 4 bytes.
    
                 The TEMPLATE is a sequence of characters that give
                 the order and type of values, as follows:
    
                     a   A string with arbitrary binary data, will be null padded.
                     A   An ascii string, will be space padded.
                     Z   A null terminated (asciz) string, will be null padded.
    
                     b   A bit string (ascending bit order inside each byte, like vec()).
                     B   A bit string (descending bit order inside each byte).
                     h   A hex string (low nybble first).
                     H   A hex string (high nybble first).
    
                     c   A signed char value.
                     C   An unsigned char value.  Only does bytes.  See U for Unicode.
    
                     s   A signed short value.
                     S   An unsigned short value.
                           (This 'short' is _exactly_ 16 bits, which may differ from
                            what a local C compiler calls 'short'.  If you want
                            native-length shorts, use the '!' suffix.)
    
                     i   A signed integer value.
                     I   An unsigned integer value.
                           (This 'integer' is _at_least_ 32 bits wide.  Its exact
                            size depends on what a local C compiler calls 'int',
                            and may even be larger than the 'long' described in
                            the next item.)
    
                     l   A signed long value.
                     L   An unsigned long value.
                           (This 'long' is _exactly_ 32 bits, which may differ from
                            what a local C compiler calls 'long'.  If you want
                            native-length longs, use the '!' suffix.)
    
                     n   An unsigned short in "network" (big-endian) order.
                     N   An unsigned long in "network" (big-endian) order.
                     v   An unsigned short in "VAX" (little-endian) order.
                     V   An unsigned long in "VAX" (little-endian) order.
                           (These 'shorts' and 'longs' are _exactly_ 16 bits and
                            _exactly_ 32 bits, respectively.)
    
                     q   A signed quad (64-bit) value.
                     Q   An unsigned quad value.
                           (Quads are available only if your system supports 64-bit
                            integer values _and_ if Perl has been compiled to support those.
                            Causes a fatal error otherwise.)
    
                     f   A single-precision float in the native format.
                     d   A double-precision float in the native format.
    
                     p   A pointer to a null-terminated string.
                     P   A pointer to a structure (fixed-length string).
    
                     u   A uuencoded string.
                     U   A Unicode character number.  Encodes to UTF-8 internally.
                         Works even if C<use utf8> is not in effect.
    
                     w   A BER compressed integer.  Its bytes represent an unsigned
                         integer in base 128, most significant digit first, with as
                         few digits as possible.  Bit eight (the high bit) is set
                         on each byte except the last.
    
                     x   A null byte.
                     X   Back up a byte.
                     @   Null fill to absolute position.
    
                 The following rules apply:
    
                 o       Each letter may optionally be followed by a
                         number giving a repeat count.  With all
                         types except `a', `A', `Z', `b', `B', `h',
                         `H', and `P' the pack function will gobble
                         up that many values from the LIST.  A `*'
                         for the repeat count means to use however
                         many items are left, except for `@', `x',
                         `X', where it is equivalent to `0', and `u',
                         where it is equivalent to 1 (or 45, what is
                         the same).
    
                         When used with `Z', `*' results in the
                         addition of a trailing null byte (so the
                         packed result will be one longer than the
                         byte `length' of the item).
    
                         The repeat count for `u' is interpreted as
                         the maximal number of bytes to encode per
                         line of output, with 0 and 1 replaced by 45.
    
                 o       The `a', `A', and `Z' types gobble just one
                         value, but pack it as a string of length
                         count, padding with nulls or spaces as
                         necessary.  When unpacking, `A' strips
                         trailing spaces and nulls, `Z' strips
                         everything after the first null, and `a'
                         returns data verbatim.  When packing, `a',
                         and `Z' are equivalent.
    
                         If the value-to-pack is too long, it is
                         truncated.  If too long and an explicit
                         count is provided, `Z' packs only `$count-1'
                         bytes, followed by a null byte.  Thus `Z'
                         always packs a trailing null byte under all
                         circumstances.
    
                 o       Likewise, the `b' and `B' fields pack a
                         string that many bits long.  Each byte of
                         the input field of pack() generates 1 bit of
                         the result.  Each result bit is based on the
                         least-significant bit of the corresponding
                         input byte, i.e., on `ord($byte)%2'.  In
                         particular, bytes `"0"' and `"1"' generate
                         bits 0 and 1, as do bytes `"\0"' and `"\1"'.
    
                         Starting from the beginning of the input
                         string of pack(), each 8-tuple of bytes is
                         converted to 1 byte of output.  With format
                         `b' the first byte of the 8-tuple determines
                         the least-significant bit of a byte, and
                         with format `B' it determines the most-
                         significant bit of a byte.
    
                         If the length of the input string is not
                         exactly divisible by 8, the remainder is
                         packed as if the input string were padded by
                         null bytes at the end.  Similarly, during
                         unpack()ing the "extra" bits are ignored.
    
                         If the input string of pack() is longer than
                         needed, extra bytes are ignored.  A `*' for
                         the repeat count of pack() means to use all
                         the bytes of the input field.  On
                         unpack()ing the bits are converted to a
                         string of `"0"'s and `"1"'s.
    
                 o       The `h' and `H' fields pack a string that
                         many nybbles (4-bit groups, representable as
                         hexadecimal digits, 0-9a-f) long.
    
                         Each byte of the input field of pack()
                         generates 4 bits of the result.  For non-
                         alphabetical bytes the result is based on
                         the 4 least-significant bits of the input
                         byte, i.e., on `ord($byte)%16'.  In
                         particular, bytes `"0"' and `"1"' generate
                         nybbles 0 and 1, as do bytes `"\0"' and
                         `"\1"'.  For bytes `"a".."f"' and `"A".."F"'
                         the result is compatible with the usual
                         hexadecimal digits, so that `"a"' and `"A"'
                         both generate the nybble `0xa==10'.  The
                         result for bytes `"g".."z"' and `"G".."Z"'
                         is not well-defined.
    
                         Starting from the beginning of the input
                         string of pack(), each pair of bytes is
                         converted to 1 byte of output.  With format
                         `h' the first byte of the pair determines
                         the least-significant nybble of the output
                         byte, and with format `H' it determines the
                         most-significant nybble.
    
                         If the length of the input string is not
                         even, it behaves as if padded by a null byte
                         at the end.  Similarly, during unpack()ing
                         the "extra" nybbles are ignored.
    
                         If the input string of pack() is longer than
                         needed, extra bytes are ignored.  A `*' for
                         the repeat count of pack() means to use all
                         the bytes of the input field.  On
                         unpack()ing the bits are converted to a
                         string of hexadecimal digits.
    
                 o       The `p' type packs a pointer to a null-
                         terminated string.  You are responsible for
                         ensuring the string is not a temporary value
                         (which can potentially get deallocated
                         before you get around to using the packed
                         result).  The `P' type packs a pointer to a
                         structure of the size indicated by the
                         length.  A NULL pointer is created if the
                         corresponding value for `p' or `P' is
                         `undef', similarly for unpack().
    
                 o       The `/' template character allows packing
                         and unpacking of strings where the packed
                         structure contains a byte count followed by
                         the string itself.  You write length-
                         item`/'string-item.
    
                         The length-item can be any `pack' template
                         letter, and describes how the length value
                         is packed.  The ones likely to be of most
                         use are integer-packing ones like `n' (for
                         Java strings), `w' (for ASN.1 or SNMP) and
                         `N' (for Sun XDR).
    
                         The string-item must, at present, be `"A*"',
                         `"a*"' or `"Z*"'.  For `unpack' the length
                         of the string is obtained from the length-
                         item, but if you put in the '*' it will be
                         ignored.
    
                             unpack 'C/a', "\04Gurusamy";        gives 'Guru'
                             unpack 'a3/A* A*', '007 Bond  J ';  gives (' Bond','J')
                             pack 'n/a* w/a*','hello,','world';  gives "\000\006hello,\005world"
    
                         The length-item is not returned explicitly
                         from `unpack'.
    
                         Adding a count to the length-item letter is
                         unlikely to do anything useful, unless that
                         letter is `A', `a' or `Z'.  Packing with a
                         length-item of `a' or `Z' may introduce
                         `"\000"' characters, which Perl does not
                         regard as legal in numeric strings.
    
                 o       The integer types `s', `S', `l', and `L' may
                         be immediately followed by a `!' suffix to
                         signify native shorts or longs--as you can
                         see from above for example a bare `l' does
                         mean exactly 32 bits, the native `long' (as
                         seen by the local C compiler) may be larger.
                         This is an issue mainly in 64-bit platforms.
                         You can see whether using `!' makes any
                         difference by
    
                                 print length(pack("s")), " ", length(pack("s!")), "\n";
                                 print length(pack("l")), " ", length(pack("l!")), "\n";
    
                         `i!' and `I!' also work but only because of
                         completeness; they are identical to `i' and
                         `I'.
    
                         The actual sizes (in bytes) of native
                         shorts, ints, longs, and long longs on the
                         platform where Perl was built are also
                         available via the Config manpage:
    
                                use Config;
                                print $Config{shortsize},    "\n";
                                print $Config{intsize},      "\n";
                                print $Config{longsize},     "\n";
                                print $Config{longlongsize}, "\n";
    
                         (The `$Config{longlongsize}' will be
                         undefine if your system does not support
                         long longs.)
    
    
                 o       The integer formats `s', `S', `i', `I', `l',
                         and `L' are inherently non-portable between
                         processors and operating systems because
                         they obey the native byteorder and
                         endianness.  For example a 4-byte integer
                         0x12345678 (305419896 decimal) be ordered
                         natively (arranged in and handled by the CPU
                         registers) into bytes as
    
                                 0x12 0x34 0x56 0x78     # little-endian
                                 0x78 0x56 0x34 0x12     # big-endian
    
                         Basically, the Intel, Alpha, and VAX CPUs
                         are little-endian, while everybody else, for
                         example Motorola m68k/88k, PPC, Sparc, HP
                         PA, Power, and Cray are big-endian.  MIPS
                         can be either: Digital used it in little-
                         endian mode; SGI uses it in big-endian mode.
    
                         The names `big-endian' and `little-endian'
                         are comic references to the classic
                         "Gulliver's Travels" (via the paper "On Holy
                         Wars and a Plea for Peace" by Danny Cohen,
                         USC/ISI IEN 137, April 1, 1980) and the
                         egg-eating habits of the Lilliputians.
    
                         Some systems may have even weirder byte
                         orders such as
    
                                 0x56 0x78 0x12 0x34
                                 0x34 0x12 0x78 0x56
    
                         You can see your system's preference with
    
                                 print join(" ", map { sprintf "%#02x", $_ }
                                                     unpack("C*",pack("L",0x12345678))), "\n";
    
                         The byteorder on the platform where Perl was
                         built is also available via the Config
                         manpage:
    
                                 use Config;
                                 print $Config{byteorder}, "\n";
    
                         Byteorders `'1234'' and `'12345678'' are
                         little-endian, `'4321'' and `'87654321'' are
                         big-endian.
    
                         If you want portable packed integers use the
                         formats `n', `N', `v', and `V', their byte
                         endianness and size is known.  See also the
                         perlport manpage.
    
                 o       Real numbers (floats and doubles) are in the
                         native machine format only; due to the
                         multiplicity of floating formats around, and
                         the lack of a standard "network"
                         representation, no facility for interchange
                         has been made.  This means that packed
                         floating point data written on one machine
                         may not be readable on another - even if
                         both use IEEE floating point arithmetic (as
                         the endian-ness of the memory representation
                         is not part of the IEEE spec).  See also the
                         perlport manpage.
    
                         Note that Perl uses doubles internally for
                         all numeric calculation, and converting from
                         double into float and thence back to double
                         again will lose precision (i.e.,
                         `unpack("f", pack("f", $foo)') will not in
                         general equal $foo).
    
                 o       You must yourself do any alignment or
                         padding by inserting for example enough
                         `'x''es while packing.  There is no way to
                         pack() and unpack() could know where the
                         bytes are going to or coming from.
                         Therefore `pack' (and `unpack') handle their
                         output and input as flat sequences of bytes.
    
                 o       A comment in a TEMPLATE starts with `#' and
                         goes to the end of line.
    
                 o       If TEMPLATE requires more arguments to
                         pack() than actually given, pack() assumes
                         additional `""' arguments.  If TEMPLATE
                         requires less arguments to pack() than
                         actually given, extra arguments are ignored.
    
                 Examples:
    
                     $foo = pack("CCCC",65,66,67,68);
                     # foo eq "ABCD"
                     $foo = pack("C4",65,66,67,68);
                     # same thing
                     $foo = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);
                     # same thing with Unicode circled letters
    
                     $foo = pack("ccxxcc",65,66,67,68);
                     # foo eq "AB\0\0CD"
    
    
    
                     # note: the above examples featuring "C" and "c" are true
                     # only on ASCII and ASCII-derived systems such as ISO Latin 1
                     # and UTF-8.  In EBCDIC the first example would be
                     # $foo = pack("CCCC",193,194,195,196);
    
                     $foo = pack("s2",1,2);
                     # "\1\0\2\0" on little-endian
                     # "\0\1\0\2" on big-endian
    
                     $foo = pack("a4","abcd","x","y","z");
                     # "abcd"
    
                     $foo = pack("aaaa","abcd","x","y","z");
                     # "axyz"
    
                     $foo = pack("a14","abcdefg");
                     # "abcdefg\0\0\0\0\0\0\0"
    
                     $foo = pack("i9pl", gmtime);
                     # a real struct tm (on my system anyway)
    
                     $utmp_template = "Z8 Z8 Z16 L";
                     $utmp = pack($utmp_template, @utmp1);
                     # a struct utmp (BSDish)
    
                     @utmp2 = unpack($utmp_template, $utmp);
                     # "@utmp1" eq "@utmp2"
    
                     sub bintodec {
                         unpack("N", pack("B32", substr("0" x 32 . shift, -32)));
                     }
    
                     $foo = pack('sx2l', 12, 34);
                     # short 12, two zero bytes padding, long 34
                     $bar = pack('s@4l', 12, 34);
                     # short 12, zero fill to position 4, long 34
                     # $foo eq $bar
    
                 The same template may generally also be used in
                 unpack().
    
         package
    
         package NAMESPACE
                 Declares the compilation unit as being in the given
                 namespace.  The scope of the package declaration is
                 from the declaration itself through the end of the
                 enclosing block, file, or eval (the same as the `my'
                 operator).  All further unqualified dynamic
                 identifiers will be in this namespace.  A package
                 statement affects only dynamic variables--including
                 those you've used `local' on--but not lexical
                 variables, which are created with `my'.  Typically
                 it would be the first declaration in a file to be
                 included by the `require' or `use' operator.  You
                 can switch into a package in more than one place; it
                 merely influences which symbol table is used by the
                 compiler for the rest of that block.  You can refer
                 to variables and filehandles in other packages by
                 prefixing the identifier with the package name and a
                 double colon:  `$Package::Variable'.  If the package
                 name is null, the `main' package as assumed.  That
                 is, `$::sail' is equivalent to `$main::sail' (as
                 well as to `$main'sail', still seen in older code).
    
                 If NAMESPACE is omitted, then there is no current
                 package, and all identifiers must be fully qualified
                 or lexicals.  This is stricter than `use strict',
                 since it also extends to function names.
    
                 See the Packages entry in the perlmod manpage for
                 more information about packages, modules, and
                 classes.  See the perlsub manpage for other scoping
                 issues.
    
         pipe READHANDLE,WRITEHANDLE
                 Opens a pair of connected pipes like the
                 corresponding system call.  Note that if you set up
                 a loop of piped processes, deadlock can occur unless
                 you are very careful.  In addition, note that Perl's
                 pipes use stdio buffering, so you may need to set
                 `$|' to flush your WRITEHANDLE after each command,
                 depending on the application.
    
                 See the IPC::Open2 manpage, the IPC::Open3 manpage,
                 and the Bidirectional Communication entry in the
                 perlipc manpage for examples of such things.
    
                 On systems that support a close-on-exec flag on
                 files, the flag will be set for the newly opened
                 file descriptors as determined by the value of $^F.
                 See the section on "$^F" in the perlvar manpage.
    
         pop ARRAY
    
         pop     Pops and returns the last value of the array,
                 shortening the array by one element.  Has an effect
                 similar to
    
                     $ARRAY[$#ARRAY--]
    
                 If there are no elements in the array, returns the
                 undefined value (although this may happen at other
                 times as well).  If ARRAY is omitted, pops the
                 `@ARGV' array in the main program, and the `@_'
                 array in subroutines, just like `shift'.
    
         pos SCALAR
    
         pos     Returns the offset of where the last `m//g' search
                 left off for the variable is in question (`$_' is
                 used when the variable is not specified).  May be
                 modified to change that offset.  Such modification
                 will also influence the `\G' zero-width assertion in
                 regular expressions.  See the perlre manpage and the
                 perlop manpage.
    
         print FILEHANDLE LIST
    
         print LIST
    
         print   Prints a string or a list of strings.  Returns true
                 if successful.  FILEHANDLE may be a scalar variable
                 name, in which case the variable contains the name
                 of or a reference to the filehandle, thus
                 introducing one level of indirection.  (NOTE: If
                 FILEHANDLE is a variable and the next token is a
                 term, it may be misinterpreted as an operator unless
                 you interpose a `+' or put parentheses around the
                 arguments.)  If FILEHANDLE is omitted, prints by
                 default to standard output (or to the last selected
                 output channel--see the select entry elsewhere in
                 this document).  If LIST is also omitted, prints
                 `$_' to the currently selected output channel.  To
                 set the default output channel to something other
                 than STDOUT use the select operation.  The current
                 value of `$,' (if any) is printed between each LIST
                 item.  The current value of `$\' (if any) is printed
                 after the entire LIST has been printed.  Because
                 print takes a LIST, anything in the LIST is
                 evaluated in list context, and any subroutine that
                 you call will have one or more of its expressions
                 evaluated in list context.  Also be careful not to
                 follow the print keyword with a left parenthesis
                 unless you want the corresponding right parenthesis
                 to terminate the arguments to the print--interpose a
                 `+' or put parentheses around all the arguments.
    
                 Note that if you're storing FILEHANDLES in an array
                 or other expression, you will have to use a block
                 returning its value instead:
    
                     print { $files[$i] } "stuff\n";
                     print { $OK ? STDOUT : STDERR } "stuff\n";
    
    
         printf FILEHANDLE FORMAT, LIST
    
         printf FORMAT, LIST
                 Equivalent to `print FILEHANDLE sprintf(FORMAT,
                 LIST)', except that `$\' (the output record
                 separator) is not appended.  The first argument of
                 the list will be interpreted as the `printf' format.
                 If `use locale' is in effect, the character used for
                 the decimal point in formatted real numbers is
                 affected by the LC_NUMERIC locale.  See the
                 perllocale manpage.
    
                 Don't fall into the trap of using a `printf' when a
                 simple `print' would do.  The `print' is more
                 efficient and less error prone.
    
         prototype FUNCTION
                 Returns the prototype of a function as a string (or
                 `undef' if the function has no prototype).  FUNCTION
                 is a reference to, or the name of, the function
                 whose prototype you want to retrieve.
    
                 If FUNCTION is a string starting with `CORE::', the
                 rest is taken as a name for Perl builtin.  If the
                 builtin is not overridable (such as `qw//') or its
                 arguments cannot be expressed by a prototype (such
                 as `system') returns `undef' because the builtin
                 does not really behave like a Perl function.
                 Otherwise, the string describing the equivalent
                 prototype is returned.
    
         push ARRAY,LIST
                 Treats ARRAY as a stack, and pushes the values of
                 LIST onto the end of ARRAY.  The length of ARRAY
                 increases by the length of LIST.  Has the same
                 effect as
    
                     for $value (LIST) {
                         $ARRAY[++$#ARRAY] = $value;
                     }
    
                 but is more efficient.  Returns the new number of
                 elements in the array.
    
         q/STRING/
    
         qq/STRING/
    
         qr/STRING/
    
         qx/STRING/
    
         qw/STRING/
                 Generalized quotes.  See the Regexp Quote-Like
                 Operators entry in the perlop manpage.
    
         quotemeta EXPR
    
         quotemeta
                 Returns the value of EXPR with all non-alphanumeric
                 characters backslashed.  (That is, all characters
                 not matching `/[A-Za-z_0-9]/' will be preceded by a
                 backslash in the returned string, regardless of any
                 locale settings.)  This is the internal function
                 implementing the `\Q' escape in double-quoted
                 strings.
    
                 If EXPR is omitted, uses `$_'.
    
         rand EXPR
    
         rand    Returns a random fractional number greater than or
                 equal to `0' and less than the value of EXPR.  (EXPR
                 should be positive.)  If EXPR is omitted, the value
                 `1' is used.  Automatically calls `srand' unless
                 `srand' has already been called.  See also `srand'.
    
                 (Note: If your rand function consistently returns
                 numbers that are too large or too small, then your
                 version of Perl was probably compiled with the wrong
                 number of RANDBITS.)
    
         read FILEHANDLE,SCALAR,LENGTH,OFFSET
    
         read FILEHANDLE,SCALAR,LENGTH
                 Attempts to read LENGTH bytes of data into variable
                 SCALAR from the specified FILEHANDLE.  Returns the
                 number of bytes actually read, `0' at end of file,
                 or undef if there was an error.  SCALAR will be
                 grown or shrunk to the length actually read.  An
                 OFFSET may be specified to place the read data at
                 some other place than the beginning of the string.
                 This call is actually implemented in terms of
                 stdio's fread(3) call.  To get a true read(2) system
                 call, see `sysread'.
    
         readdir DIRHANDLE
                 Returns the next directory entry for a directory
                 opened by `opendir'.  If used in list context,
                 returns all the rest of the entries in the
                 directory.  If there are no more entries, returns an
                 undefined value in scalar context or a null list in
                 list context.
    
                 If you're planning to filetest the return values out
                 of a `readdir', you'd better prepend the directory
                 in question.  Otherwise, because we didn't `chdir'
                 there, it would have been testing the wrong file.
    
                     opendir(DIR, $some_dir) || die "can't opendir $some_dir: $!";
                     @dots = grep { /^\./ && -f "$some_dir/$_" } readdir(DIR);
                     closedir DIR;
    
    
         readline EXPR
                 Reads from the filehandle whose typeglob is
                 contained in EXPR.  In scalar context, each call
                 reads and returns the next line, until end-of-file
                 is reached, whereupon the subsequent call returns
                 undef.  In list context, reads until end-of-file is
                 reached and returns a list of lines.  Note that the
                 notion of "line" used here is however you may have
                 defined it with `$/' or `$INPUT_RECORD_SEPARATOR').
                 See the section on "$/" in the perlvar manpage.
    
                 When `$/' is set to `undef', when readline() is in
                 scalar context (i.e. file slurp mode), and when an
                 empty file is read, it returns `''' the first time,
                 followed by `undef' subsequently.
    
                 This is the internal function implementing the
                 `<EXPR>' operator, but you can use it directly.  The
                 `<EXPR>' operator is discussed in more detail in the
                 I/O Operators entry in the perlop manpage.
    
                     $line = <STDIN>;
                     $line = readline(*STDIN);           # same thing
    
    
         readlink EXPR
    
         readlink
                 Returns the value of a symbolic link, if symbolic
                 links are implemented.  If not, gives a fatal error.
                 If there is some system error, returns the undefined
                 value and sets `$!' (errno).  If EXPR is omitted,
                 uses `$_'.
    
         readpipe EXPR
                 EXPR is executed as a system command.  The collected
                 standard output of the command is returned.  In
                 scalar context, it comes back as a single
                 (potentially multi-line) string.  In list context,
                 returns a list of lines (however you've defined
                 lines with `$/' or `$INPUT_RECORD_SEPARATOR').  This
                 is the internal function implementing the `qx/EXPR/'
                 operator, but you can use it directly.  The
                 `qx/EXPR/' operator is discussed in more detail in
                 the I/O Operators entry in the perlop manpage.
    
         recv SOCKET,SCALAR,LENGTH,FLAGS
                 Receives a message on a socket.  Attempts to receive
                 LENGTH bytes of data into variable SCALAR from the
                 specified SOCKET filehandle.  SCALAR will be grown
                 or shrunk to the length actually read.  Takes the
                 same flags as the system call of the same name.
                 Returns the address of the sender if SOCKET's
                 protocol supports this; returns an empty string
                 otherwise.  If there's an error, returns the
                 undefined value.  This call is actually implemented
                 in terms of recvfrom(2) system call.  See the UDP:
                 Message Passing entry in the perlipc manpage for
                 examples.
    
         redo LABEL
    
         redo    The `redo' command restarts the loop block without
                 evaluating the conditional again.  The `continue'
                 block, if any, is not executed.  If the LABEL is
                 omitted, the command refers to the innermost
                 enclosing loop.  This command is normally used by
                 programs that want to lie to themselves about what
                 was just input:
    
                     # a simpleminded Pascal comment stripper
                     # (warning: assumes no { or } in strings)
                     LINE: while (<STDIN>) {
                         while (s|({.*}.*){.*}|$1 |) {}
                         s|{.*}| |;
                         if (s|{.*| |) {
                             $front = $_;
                             while (<STDIN>) {
                                 if (/}/) {      # end of comment?
                                     s|^|$front\{|;
                                     redo LINE;
                                 }
                             }
                         }
                         print;
                     }
    
                 `redo' cannot be used to retry a block which returns
                 a value such as `eval {}', `sub {}' or `do {}', and
                 should not be used to exit a grep() or map()
                 operation.
    
                 Note that a block by itself is semantically
                 identical to a loop that executes once.  Thus `redo'
                 inside such a block will effectively turn it into a
                 looping construct.
    
                 See also the continue entry elsewhere in this
                 document for an illustration of how `last', `next',
                 and `redo' work.
    
         ref EXPR
    
         ref     Returns a true value if EXPR is a reference, false
                 otherwise.  If EXPR is not specified, `$_' will be
                 used.  The value returned depends on the type of
                 thing the reference is a reference to.  Builtin
                 types include:
    
                     SCALAR
                     ARRAY
                     HASH
                     CODE
                     REF
                     GLOB
                     LVALUE
    
                 If the referenced object has been blessed into a
                 package, then that package name is returned instead.
                 You can think of `ref' as a `typeof' operator.
    
                     if (ref($r) eq "HASH") {
                         print "r is a reference to a hash.\n";
                     }
                     unless (ref($r)) {
                         print "r is not a reference at all.\n";
                     }
                     if (UNIVERSAL::isa($r, "HASH")) {  # for subclassing
                         print "r is a reference to something that isa hash.\n";
                     }
    
                 See also the perlref manpage.
    
         rename OLDNAME,NEWNAME
                 Changes the name of a file; an existing file NEWNAME
                 will be clobbered.  Returns true for success, false
                 otherwise.
    
                 Behavior of this function varies wildly depending on
                 your system implementation.  For example, it will
                 usually not work across file system boundaries, even
                 though the system mv command sometimes compensates
                 for this.  Other restrictions include whether it
                 works on directories, open files, or pre-existing
                 files.  Check the perlport manpage and either the
                 rename(2) manpage or equivalent system documentation
                 for details.
    
         require VERSION
    
         require EXPR
    
         require Demands some semantics specified by EXPR, or by `$_'
                 if EXPR is not supplied.
    
                 If a VERSION is specified as a literal of the form
                 v5.6.1, demands that the current version of Perl
                 (`$^V' or $PERL_VERSION) be at least as recent as
                 that version, at run time.  (For compatibility with
                 older versions of Perl, a numeric argument will also
                 be interpreted as VERSION.)  Compare with the use
                 entry elsewhere in this document, which can do a
                 similar check at compile time.
    
                     require v5.6.1;     # run time version check
                     require 5.6.1;      # ditto
                     require 5.005_03;   # float version allowed for compatibility
    
                 Otherwise, demands that a library file be included
                 if it hasn't already been included.  The file is
                 included via the do-FILE mechanism, which is
                 essentially just a variety of `eval'.  Has semantics
                 similar to the following subroutine:
    
                     sub require {
                         my($filename) = @_;
                         return 1 if $INC{$filename};
                         my($realfilename,$result);
                         ITER: {
                             foreach $prefix (@INC) {
                                 $realfilename = "$prefix/$filename";
                                 if (-f $realfilename) {
                                     $INC{$filename} = $realfilename;
                                     $result = do $realfilename;
                                     last ITER;
                                 }
                             }
                             die "Can't find $filename in \@INC";
                         }
                         delete $INC{$filename} if $@ || !$result;
                         die $@ if $@;
                         die "$filename did not return true value" unless $result;
                         return $result;
                     }
    
                 Note that the file will not be included twice under
                 the same specified name.  The file must return true
                 as the last statement to indicate successful
                 execution of any initialization code, so it's
                 customary to end such a file with `1;' unless you're
                 sure it'll return true otherwise.  But it's better
                 just to put the `1;', in case you add more
                 statements.
    
                 If EXPR is a bareword, the require assumes a ".pm"
                 extension and replaces "::" with "/" in the filename
                 for you, to make it easy to load standard modules.
                 This form of loading of modules does not risk
                 altering your namespace.
    
                 In other words, if you try this:
    
                         require Foo::Bar;    # a splendid bareword
    
                 The require function will actually look for the
                 "Foo/Bar.pm" file in the directories specified in
                 the `@INC' array.
    
                 But if you try this:
    
                         $class = 'Foo::Bar';
                         require $class;      # $class is not a bareword
                     #or
                         require "Foo::Bar";  # not a bareword because of the ""
    
                 The require function will look for the "Foo::Bar"
                 file in the @INC array and will complain about not
                 finding "Foo::Bar" there.  In this case you can do:
    
                         eval "require $class";
    
                 For a yet-more-powerful import facility, see the use
                 entry elsewhere in this document and the perlmod
                 manpage.
    
         reset EXPR
    
         reset   Generally used in a `continue' block at the end of a
                 loop to clear variables and reset `??' searches so
                 that they work again.  The expression is interpreted
                 as a list of single characters (hyphens allowed for
                 ranges).  All variables and arrays beginning with
                 one of those letters are reset to their pristine
                 state.  If the expression is omitted, one-match
                 searches (`?pattern?') are reset to match again.
                 Resets only variables or searches in the current
                 package.  Always returns 1.  Examples:
    
    
    
                     reset 'X';          # reset all X variables
                     reset 'a-z';        # reset lower case variables
                     reset;              # just reset ?one-time? searches
    
                 Resetting `"A-Z"' is not recommended because you'll
                 wipe out your `@ARGV' and `@INC' arrays and your
                 `%ENV' hash.  Resets only package variables--lexical
                 variables are unaffected, but they clean themselves
                 up on scope exit anyway, so you'll probably want to
                 use them instead.  See the my entry elsewhere in
                 this document.
    
         return EXPR
    
         return  Returns from a subroutine, `eval', or `do FILE' with
                 the value given in EXPR.  Evaluation of EXPR may be
                 in list, scalar, or void context, depending on how
                 the return value will be used, and the context may
                 vary from one execution to the next (see
                 `wantarray').  If no EXPR is given, returns an empty
                 list in list context, the undefined value in scalar
                 context, and (of course) nothing at all in a void
                 context.
    
                 (Note that in the absence of a explicit `return', a
                 subroutine, eval, or do FILE will automatically
                 return the value of the last expression evaluated.)
    
         reverse LIST
                 In list context, returns a list value consisting of
                 the elements of LIST in the opposite order.  In
                 scalar context, concatenates the elements of LIST
                 and returns a string value with all characters in
                 the opposite order.
    
                     print reverse <>;           # line tac, last line first
    
                     undef $/;                   # for efficiency of <>
                     print scalar reverse <>;    # character tac, last line tsrif
    
                 This operator is also handy for inverting a hash,
                 although there are some caveats.  If a value is
                 duplicated in the original hash, only one of those
                 can be represented as a key in the inverted hash.
                 Also, this has to unwind one hash and build a whole
                 new one, which may take some time on a large hash,
                 such as from a DBM file.
    
                     %by_name = reverse %by_address;     # Invert the hash
    
    
    
         rewinddir DIRHANDLE
                 Sets the current position to the beginning of the
                 directory for the `readdir' routine on DIRHANDLE.
    
         rindex STR,SUBSTR,POSITION
    
         rindex STR,SUBSTR
                 Works just like index() except that it returns the
                 position of the LAST occurrence of SUBSTR in STR.
                 If POSITION is specified, returns the last
                 occurrence at or before that position.
    
         rmdir FILENAME
    
         rmdir   Deletes the directory specified by FILENAME if that
                 directory is empty.  If it succeeds it returns true,
                 otherwise it returns false and sets `$!' (errno).
                 If FILENAME is omitted, uses `$_'.
    
         s///    The substitution operator.  See the perlop manpage.
    
         scalar EXPR
                 Forces EXPR to be interpreted in scalar context and
                 returns the value of EXPR.
    
                     @counts = ( scalar @a, scalar @b, scalar @c );
    
                 There is no equivalent operator to force an
                 expression to be interpolated in list context
                 because in practice, this is never needed.  If you
                 really wanted to do so, however, you could use the
                 construction `@{[ (some expression) ]}', but usually
                 a simple `(some expression)' suffices.
    
                 Because `scalar' is unary operator, if you
                 accidentally use for EXPR a parenthesized list, this
                 behaves as a scalar comma expression, evaluating all
                 but the last element in void context and returning
                 the final element evaluated in scalar context.  This
                 is seldom what you want.
    
                 The following single statement:
    
                         print uc(scalar(&foo,$bar)),$baz;
    
                 is the moral equivalent of these two:
    
                         &foo;
                         print(uc($bar),$baz);
    
                 See the perlop manpage for more details on unary
                 operators and the comma operator.
    
         seek FILEHANDLE,POSITION,WHENCE
                 Sets FILEHANDLE's position, just like the `fseek'
                 call of `stdio'.  FILEHANDLE may be an expression
                 whose value gives the name of the filehandle.  The
                 values for WHENCE are `0' to set the new position to
                 POSITION, `1' to set it to the current position plus
                 POSITION, and `2' to set it to EOF plus POSITION
                 (typically negative).  For WHENCE you may use the
                 constants `SEEK_SET', `SEEK_CUR', and `SEEK_END'
                 (start of the file, current position, end of the
                 file) from the Fcntl module.  Returns `1' upon
                 success, `0' otherwise.
    
                 If you want to position file for `sysread' or
                 `syswrite', don't use `seek'--buffering makes its
                 effect on the file's system position unpredictable
                 and non-portable.  Use `sysseek' instead.
    
                 Due to the rules and rigors of ANSI C, on some
                 systems you have to do a seek whenever you switch
                 between reading and writing.  Amongst other things,
                 this may have the effect of calling stdio's
                 clearerr(3).  A WHENCE of `1' (`SEEK_CUR') is useful
                 for not moving the file position:
    
                     seek(TEST,0,1);
    
                 This is also useful for applications emulating `tail
                 -f'.  Once you hit EOF on your read, and then sleep
                 for a while, you might have to stick in a seek() to
                 reset things.  The `seek' doesn't change the current
                 position, but it does clear the end-of-file
                 condition on the handle, so that the next `<FILE>'
                 makes Perl try again to read something.  We hope.
    
                 If that doesn't work (some stdios are particularly
                 cantankerous), then you may need something more like
                 this:
    
                     for (;;) {
                         for ($curpos = tell(FILE); $_ = <FILE>;
                              $curpos = tell(FILE)) {
                             # search for some stuff and put it into files
                         }
                         sleep($for_a_while);
                         seek(FILE, $curpos, 0);
                     }
    
    
         seekdir DIRHANDLE,POS
                 Sets the current position for the `readdir' routine
                 on DIRHANDLE.  POS must be a value returned by
                 `telldir'.  Has the same caveats about possible
                 directory compaction as the corresponding system
                 library routine.
    
         select FILEHANDLE
    
         select  Returns the currently selected filehandle.  Sets the
                 current default filehandle for output, if FILEHANDLE
                 is supplied.  This has two effects: first, a `write'
                 or a `print' without a filehandle will default to
                 this FILEHANDLE.  Second, references to variables
                 related to output will refer to this output channel.
                 For example, if you have to set the top of form
                 format for more than one output channel, you might
                 do the following:
    
                     select(REPORT1);
                     $^ = 'report1_top';
                     select(REPORT2);
                     $^ = 'report2_top';
    
                 FILEHANDLE may be an expression whose value gives
                 the name of the actual filehandle.  Thus:
    
                     $oldfh = select(STDERR); $| = 1; select($oldfh);
    
                 Some programmers may prefer to think of filehandles
                 as objects with methods, preferring to write the
                 last example as:
    
                     use IO::Handle;
                     STDERR->autoflush(1);
    
    
         select RBITS,WBITS,EBITS,TIMEOUT
                 This calls the select(2) system call with the bit
                 masks specified, which can be constructed using
                 `fileno' and `vec', along these lines:
    
                     $rin = $win = $ein = '';
                     vec($rin,fileno(STDIN),1) = 1;
                     vec($win,fileno(STDOUT),1) = 1;
                     $ein = $rin | $win;
    
                 If you want to select on many filehandles you might
                 wish to write a subroutine:
    
    
    
                     sub fhbits {
                         my(@fhlist) = split(' ',$_[0]);
                         my($bits);
                         for (@fhlist) {
                             vec($bits,fileno($_),1) = 1;
                         }
                         $bits;
                     }
                     $rin = fhbits('STDIN TTY SOCK');
    
                 The usual idiom is:
    
                     ($nfound,$timeleft) =
                       select($rout=$rin, $wout=$win, $eout=$ein, $timeout);
    
                 or to block until something becomes ready just do
                 this
    
                     $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef);
    
                 Most systems do not bother to return anything useful
                 in $timeleft, so calling select() in scalar context
                 just returns $nfound.
    
                 Any of the bit masks can also be undef.  The
                 timeout, if specified, is in seconds, which may be
                 fractional.  Note: not all implementations are
                 capable of returning the$timeleft.  If not, they
                 always return $timeleft equal to the supplied
                 $timeout.
    
                 You can effect a sleep of 250 milliseconds this way:
    
                     select(undef, undef, undef, 0.25);
    
                 WARNING: One should not attempt to mix buffered I/O
                 (like `read' or <FH>) with `select', except as
                 permitted by POSIX, and even then only on POSIX
                 systems.  You have to use `sysread' instead.
    
         semctl ID,SEMNUM,CMD,ARG
                 Calls the System V IPC function `semctl'.  You'll
                 probably have to say
    
                     use IPC::SysV;
    
                 first to get the correct constant definitions.  If
                 CMD is IPC_STAT or GETALL, then ARG must be a
                 variable which will hold the returned semid_ds
                 structure or semaphore value array.  Returns like
                 `ioctl':  the undefined value for error, "`0 but
                 true'" for zero, or the actual return value
                 otherwise.  The ARG must consist of a vector of
                 native short integers, which may may be created with
                 `pack("s!",(0)x$nsem)'.  See also `IPC::SysV' and
                 `IPC::Semaphore' documentation.
    
         semget KEY,NSEMS,FLAGS
                 Calls the System V IPC function semget.  Returns the
                 semaphore id, or the undefined value if there is an
                 error.  See also `IPC::SysV' and
                 `IPC::SysV::Semaphore' documentation.
    
         semop KEY,OPSTRING
                 Calls the System V IPC function semop to perform
                 semaphore operations such as signaling and waiting.
                 OPSTRING must be a packed array of semop structures.
                 Each semop structure can be generated with
                 `pack("sss", $semnum, $semop, $semflag)'.  The
                 number of semaphore operations is implied by the
                 length of OPSTRING.  Returns true if successful, or
                 false if there is an error.  As an example, the
                 following code waits on semaphore $semnum of
                 semaphore id $semid:
    
                     $semop = pack("sss", $semnum, -1, 0);
                     die "Semaphore trouble: $!\n" unless semop($semid, $semop);
    
                 To signal the semaphore, replace `-1' with `1'.  See
                 also `IPC::SysV' and `IPC::SysV::Semaphore'
                 documentation.
    
         send SOCKET,MSG,FLAGS,TO
    
         send SOCKET,MSG,FLAGS
                 Sends a message on a socket.  Takes the same flags
                 as the system call of the same name.  On unconnected
                 sockets you must specify a destination to send TO,
                 in which case it does a C `sendto'.  Returns the
                 number of characters sent, or the undefined value if
                 there is an error.  The C system call sendmsg(2) is
                 currently unimplemented.  See the UDP: Message
                 Passing entry in the perlipc manpage for examples.
    
         setpgrp PID,PGRP
                 Sets the current process group for the specified
                 PID, `0' for the current process.  Will produce a
                 fatal error if used on a machine that doesn't
                 implement POSIX setpgid(2) or BSD setpgrp(2).  If
                 the arguments are omitted, it defaults to `0,0'.
                 Note that the BSD 4.2 version of `setpgrp' does not
                 accept any arguments, so only `setpgrp(0,0)' is
                 portable.  See also `POSIX::setsid()'.
    
         setpriority WHICH,WHO,PRIORITY
                 Sets the current priority for a process, a process
                 group, or a user.  (See setpriority(2).)  Will
                 produce a fatal error if used on a machine that
                 doesn't implement setpriority(2).
    
         setsockopt SOCKET,LEVEL,OPTNAME,OPTVAL
                 Sets the socket option requested.  Returns undefined
                 if there is an error.  OPTVAL may be specified as
                 `undef' if you don't want to pass an argument.
    
         shift ARRAY
    
         shift   Shifts the first value of the array off and returns
                 it, shortening the array by 1 and moving everything
                 down.  If there are no elements in the array,
                 returns the undefined value.  If ARRAY is omitted,
                 shifts the `@_' array within the lexical scope of
                 subroutines and formats, and the `@ARGV' array at
                 file scopes or within the lexical scopes established
                 by the `eval ''', `BEGIN {}', `INIT {}', `CHECK {}',
                 and `END {}' constructs.
    
                 See also `unshift', `push', and `pop'.  `Shift()'
                 and `unshift' do the same thing to the left end of
                 an array that `pop' and `push' do to the right end.
    
         shmctl ID,CMD,ARG
                 Calls the System V IPC function shmctl.  You'll
                 probably have to say
    
                     use IPC::SysV;
    
                 first to get the correct constant definitions.  If
                 CMD is `IPC_STAT', then ARG must be a variable which
                 will hold the returned `shmid_ds' structure.
                 Returns like ioctl: the undefined value for error,
                 "`0' but true" for zero, or the actual return value
                 otherwise.  See also `IPC::SysV' documentation.
    
         shmget KEY,SIZE,FLAGS
                 Calls the System V IPC function shmget.  Returns the
                 shared memory segment id, or the undefined value if
                 there is an error.  See also `IPC::SysV'
                 documentation.
    
         shmread ID,VAR,POS,SIZE
    
         shmwrite ID,STRING,POS,SIZE
                 Reads or writes the System V shared memory segment
                 ID starting at position POS for size SIZE by
                 attaching to it, copying in/out, and detaching from
                 it.  When reading, VAR must be a variable that will
                 hold the data read.  When writing, if STRING is too
                 long, only SIZE bytes are used; if STRING is too
                 short, nulls are written to fill out SIZE bytes.
                 Return true if successful, or false if there is an
                 error.  shmread() taints the variable. See also
                 `IPC::SysV' documentation and the `IPC::Shareable'
                 module from CPAN.
    
         shutdown SOCKET,HOW
                 Shuts down a socket connection in the manner
                 indicated by HOW, which has the same interpretation
                 as in the system call of the same name.
    
                     shutdown(SOCKET, 0);    # I/we have stopped reading data
                     shutdown(SOCKET, 1);    # I/we have stopped writing data
                     shutdown(SOCKET, 2);    # I/we have stopped using this socket
    
                 This is useful with sockets when you want to tell
                 the other side you're done writing but not done
                 reading, or vice versa.  It's also a more insistent
                 form of close because it also disables the file
                 descriptor in any forked copies in other processes.
    
         sin EXPR
    
         sin     Returns the sine of EXPR (expressed in radians).  If
                 EXPR is omitted, returns sine of `$_'.
    
                 For the inverse sine operation, you may use the
                 `Math::Trig::asin' function, or use this relation:
    
                     sub asin { atan2($_[0], sqrt(1 - $_[0] * $_[0])) }
    
    
         sleep EXPR
    
         sleep   Causes the script to sleep for EXPR seconds, or
                 forever if no EXPR.  May be interrupted if the
                 process receives a signal such as `SIGALRM'.
                 Returns the number of seconds actually slept.  You
                 probably cannot mix `alarm' and `sleep' calls,
                 because `sleep' is often implemented using `alarm'.
    
                 On some older systems, it may sleep up to a full
                 second less than what you requested, depending on
                 how it counts seconds.  Most modern systems always
                 sleep the full amount.  They may appear to sleep
                 longer than that, however, because your process
                 might not be scheduled right away in a busy
                 multitasking system.
    
                 For delays of finer granularity than one second, you
                 may use Perl's `syscall' interface to access
                 setitimer(2) if your system supports it, or else see
                 the select entry elsewhere in this document above.
                 The Time::HiRes module from CPAN may also help.
    
                 See also the POSIX module's `sigpause' function.
    
         socket SOCKET,DOMAIN,TYPE,PROTOCOL
                 Opens a socket of the specified kind and attaches it
                 to filehandle SOCKET.  DOMAIN, TYPE, and PROTOCOL
                 are specified the same as for the system call of the
                 same name.  You should `use Socket' first to get the
                 proper definitions imported.  See the examples in
                 the Sockets: Client/Server Communication entry in
                 the perlipc manpage.
    
                 On systems that support a close-on-exec flag on
                 files, the flag will be set for the newly opened
                 file descriptor, as determined by the value of $^F.
                 See the section on "$^F" in the perlvar manpage.
    
         socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
                 Creates an unnamed pair of sockets in the specified
                 domain, of the specified type.  DOMAIN, TYPE, and
                 PROTOCOL are specified the same as for the system
                 call of the same name.  If unimplemented, yields a
                 fatal error.  Returns true if successful.
    
                 On systems that support a close-on-exec flag on
                 files, the flag will be set for the newly opened
                 file descriptors, as determined by the value of $^F.
                 See the section on "$^F" in the perlvar manpage.
    
                 Some systems defined `pipe' in terms of
                 `socketpair', in which a call to `pipe(Rdr, Wtr)' is
                 essentially:
    
                     use Socket;
                     socketpair(Rdr, Wtr, AF_UNIX, SOCK_STREAM, PF_UNSPEC);
                     shutdown(Rdr, 1);        # no more writing for reader
                     shutdown(Wtr, 0);        # no more reading for writer
    
                 See the perlipc manpage for an example of socketpair
                 use.
    
         sort SUBNAME LIST
    
         sort BLOCK LIST
    
         sort LIST
                 Sorts the LIST and returns the sorted list value.
                 If SUBNAME or BLOCK is omitted, `sort's in standard
                 string comparison order.  If SUBNAME is specified,
                 it gives the name of a subroutine that returns an
                 integer less than, equal to, or greater than `0',
                 depending on how the elements of the list are to be
                 ordered.  (The `<=>' and `cmp' operators are
                 extremely useful in such routines.)  SUBNAME may be
                 a scalar variable name (unsubscripted), in which
                 case the value provides the name of (or a reference
                 to) the actual subroutine to use.  In place of a
                 SUBNAME, you can provide a BLOCK as an anonymous,
                 in-line sort subroutine.
    
                 If the subroutine's prototype is `($$)', the
                 elements to be compared are passed by reference in
                 `@_', as for a normal subroutine.  This is slower
                 than unprototyped subroutines, where the elements to
                 be compared are passed into the subroutine as the
                 package global variables $a and $b (see example
                 below).  Note that in the latter case, it is usually
                 counter-productive to declare $a and $b as lexicals.
    
                 In either case, the subroutine may not be recursive.
                 The values to be compared are always passed by
                 reference, so don't modify them.
    
                 You also cannot exit out of the sort block or
                 subroutine using any of the loop control operators
                 described in the perlsyn manpage or with `goto'.
    
                 When `use locale' is in effect, `sort LIST' sorts
                 LIST according to the current collation locale.  See
                 the perllocale manpage.
    
                 Examples:
    
                     # sort lexically
                     @articles = sort @files;
    
                     # same thing, but with explicit sort routine
                     @articles = sort {$a cmp $b} @files;
    
                     # now case-insensitively
                     @articles = sort {uc($a) cmp uc($b)} @files;
    
                     # same thing in reversed order
                     @articles = sort {$b cmp $a} @files;
    
                     # sort numerically ascending
                     @articles = sort {$a <=> $b} @files;
    
    
                     # sort numerically descending
                     @articles = sort {$b <=> $a} @files;
    
                     # this sorts the %age hash by value instead of key
                     # using an in-line function
                     @eldest = sort { $age{$b} <=> $age{$a} } keys %age;
    
                     # sort using explicit subroutine name
                     sub byage {
                         $age{$a} <=> $age{$b};  # presuming numeric
                     }
                     @sortedclass = sort byage @class;
    
                     sub backwards { $b cmp $a }
                     @harry  = qw(dog cat x Cain Abel);
                     @george = qw(gone chased yz Punished Axed);
                     print sort @harry;
                             # prints AbelCaincatdogx
                     print sort backwards @harry;
                             # prints xdogcatCainAbel
                     print sort @george, 'to', @harry;
                             # prints AbelAxedCainPunishedcatchaseddoggonetoxyz
    
                     # inefficiently sort by descending numeric compare using
                     # the first integer after the first = sign, or the
                     # whole record case-insensitively otherwise
    
                     @new = sort {
                         ($b =~ /=(\d+)/)[0] <=> ($a =~ /=(\d+)/)[0]
                                             ||
                                     uc($a)  cmp  uc($b)
                     } @old;
    
                     # same thing, but much more efficiently;
                     # we'll build auxiliary indices instead
                     # for speed
                     @nums = @caps = ();
                     for (@old) {
                         push @nums, /=(\d+)/;
                         push @caps, uc($_);
                     }
    
                     @new = @old[ sort {
                                         $nums[$b] <=> $nums[$a]
                                                  ||
                                         $caps[$a] cmp $caps[$b]
                                        } 0..$#old
                                ];
    
    
    
                     # same thing, but without any temps
                     @new = map { $_->[0] }
                            sort { $b->[1] <=> $a->[1]
                                            ||
                                   $a->[2] cmp $b->[2]
                            } map { [$_, /=(\d+)/, uc($_)] } @old;
    
                     # using a prototype allows you to use any comparison subroutine
                     # as a sort subroutine (including other package's subroutines)
                     package other;
                     sub backwards ($$) { $_[1] cmp $_[0]; }     # $a and $b are not set here
    
                     package main;
                     @new = sort other::backwards @old;
    
                 If you're using strict, you must not declare $a and
                 $b as lexicals.  They are package globals.  That
                 means if you're in the `main' package, it's
    
                     @articles = sort {$main::b <=> $main::a} @files;
    
                 or just
    
                     @articles = sort {$::b <=> $::a} @files;
    
                 but if you're in the `FooPack' package, it's
    
                     @articles = sort {$FooPack::b <=> $FooPack::a} @files;
    
                 The comparison function is required to behave.  If
                 it returns inconsistent results (sometimes saying
                 `$x[1]' is less than `$x[2]' and sometimes saying
                 the opposite, for example) the results are not
                 well-defined.
    
         splice ARRAY,OFFSET,LENGTH,LIST
    
         splice ARRAY,OFFSET,LENGTH
    
         splice ARRAY,OFFSET
    
         splice ARRAY
                 Removes the elements designated by OFFSET and LENGTH
                 from an array, and replaces them with the elements
                 of LIST, if any.  In list context, returns the
                 elements removed from the array.  In scalar context,
                 returns the last element removed, or `undef' if no
                 elements are removed.  The array grows or shrinks as
                 necessary.  If OFFSET is negative then it starts
                 that far from the end of the array.  If LENGTH is
                 omitted, removes everything from OFFSET onward.  If
                 LENGTH is negative, leaves that many elements off
                 the end of the array.  If both OFFSET and LENGTH are
                 omitted, removes everything.
    
                 The following equivalences hold (assuming `$[ ==
                 0'):
    
                     push(@a,$x,$y)      splice(@a,@a,0,$x,$y)
                     pop(@a)             splice(@a,-1)
                     shift(@a)           splice(@a,0,1)
                     unshift(@a,$x,$y)   splice(@a,0,0,$x,$y)
                     $a[$x] = $y         splice(@a,$x,1,$y)
    
                 Example, assuming array lengths are passed before
                 arrays:
    
                     sub aeq {   # compare two list values
                         my(@a) = splice(@_,0,shift);
                         my(@b) = splice(@_,0,shift);
                         return 0 unless @a == @b;       # same len?
                         while (@a) {
                             return 0 if pop(@a) ne pop(@b);
                         }
                         return 1;
                     }
                     if (&aeq($len,@foo[1..$len],0+@bar,@bar)) { ... }
    
    
         split /PATTERN/,EXPR,LIMIT
    
         split /PATTERN/,EXPR
    
         split /PATTERN/
    
         split   Splits a string into a list of strings and returns
                 that list.  By default, empty leading fields are
                 preserved, and empty trailing ones are deleted.
    
                 If not in list context, returns the number of fields
                 found and splits into the `@_' array.  (In list
                 context, you can force the split into `@_' by using
                 `??' as the pattern delimiters, but it still returns
                 the list value.)  The use of implicit split to `@_'
                 is deprecated, however, because it clobbers your
                 subroutine arguments.
    
                 If EXPR is omitted, splits the `$_' string.  If
                 PATTERN is also omitted, splits on whitespace (after
                 skipping any leading whitespace).  Anything matching
                 PATTERN is taken to be a delimiter separating the
                 fields.  (Note that the delimiter may be longer than
                 one character.)
    
                 If LIMIT is specified and positive, splits into no
                 more than that many fields (though it may split into
                 fewer).  If LIMIT is unspecified or zero, trailing
                 null fields are stripped (which potential users of
                 `pop' would do well to remember).  If LIMIT is
                 negative, it is treated as if an arbitrarily large
                 LIMIT had been specified.
    
                 A pattern matching the null string (not to be
                 confused with a null pattern `//', which is just one
                 member of the set of patterns matching a null
                 string) will split the value of EXPR into separate
                 characters at each point it matches that way.  For
                 example:
    
                     print join(':', split(/ */, 'hi there'));
    
                 produces the output 'h:i:t:h:e:r:e'.
    
                 The LIMIT parameter can be used to split a line
                 partially
    
                     ($login, $passwd, $remainder) = split(/:/, $_, 3);
    
                 When assigning to a list, if LIMIT is omitted, Perl
                 supplies a LIMIT one larger than the number of
                 variables in the list, to avoid unnecessary work.
                 For the list above LIMIT would have been 4 by
                 default.  In time critical applications it behooves
                 you not to split into more fields than you really
                 need.
    
                 If the PATTERN contains parentheses, additional list
                 elements are created from each matching substring in
                 the delimiter.
    
                     split(/([,-])/, "1-10,20", 3);
    
                 produces the list value
    
                     (1, '-', 10, ',', 20)
    
                 If you had the entire header of a normal Unix email
                 message in $header, you could split it up into
                 fields and their values this way:
    
                     $header =~ s/\n\s+/ /g;  # fix continuation lines
                     %hdrs   =  (UNIX_FROM => split /^(\S*?):\s*/m, $header);
    
                 The pattern `/PATTERN/' may be replaced with an
                 expression to specify patterns that vary at runtime.
                 (To do runtime compilation only once, use
                 `/$variable/o'.)
    
                 As a special case, specifying a PATTERN of space (`'
                 '') will split on white space just as `split' with
                 no arguments does.  Thus, `split(' ')' can be used
                 to emulate awk's default behavior, whereas `split(/
                 /)' will give you as many null initial fields as
                 there are leading spaces.  A `split' on `/\s+/' is
                 like a `split(' ')' except that any leading
                 whitespace produces a null first field.  A `split'
                 with no arguments really does a `split(' ', $_)'
                 internally.
    
                 Example:
    
                     open(PASSWD, '/etc/passwd');
                     while (<PASSWD>) {
                         ($login, $passwd, $uid, $gid,
                          $gcos, $home, $shell) = split(/:/);
                         #...
                     }
    
                 (Note that $shell above will still have a newline on
                 it.  See the chop, chomp, and join entries elsewhere
                 in this document.)
    
         sprintf FORMAT, LIST
                 Returns a string formatted by the usual `printf'
                 conventions of the C library function `sprintf'.
                 See sprintf(3) or printf(3) on your system for an
                 explanation of the general principles.
    
                 Perl does its own `sprintf' formatting--it emulates
                 the C function `sprintf', but it doesn't use it
                 (except for floating-point numbers, and even then
                 only the standard modifiers are allowed).  As a
                 result, any non-standard extensions in your local
                 `sprintf' are not available from Perl.
    
                 Perl's `sprintf' permits the following universally-
                 known conversions:
    
                    %%   a percent sign
                    %c   a character with the given number
                    %s   a string
                    %d   a signed integer, in decimal
                    %u   an unsigned integer, in decimal
                    %o   an unsigned integer, in octal
                    %x   an unsigned integer, in hexadecimal
                    %e   a floating-point number, in scientific notation
                    %f   a floating-point number, in fixed decimal notation
                    %g   a floating-point number, in %e or %f notation
    
                 In addition, Perl permits the following widely-
                 supported conversions:
    
                    %X   like %x, but using upper-case letters
                    %E   like %e, but using an upper-case "E"
                    %G   like %g, but with an upper-case "E" (if applicable)
                    %b   an unsigned integer, in binary
                    %p   a pointer (outputs the Perl value's address in hexadecimal)
                    %n   special: *stores* the number of characters output so far
                         into the next variable in the parameter list
    
                 Finally, for backward (and we do mean "backward")
                 compatibility, Perl permits these unnecessary but
                 widely-supported conversions:
    
                    %i   a synonym for %d
                    %D   a synonym for %ld
                    %U   a synonym for %lu
                    %O   a synonym for %lo
                    %F   a synonym for %f
    
                 Perl permits the following universally-known flags
                 between the `%' and the conversion letter:
    
                    space   prefix positive number with a space
                    +       prefix positive number with a plus sign
                    -       left-justify within the field
                    0       use zeros, not spaces, to right-justify
                    #       prefix non-zero octal with "0", non-zero hex with "0x"
                    number  minimum field width
                    .number "precision": digits after decimal point for
                            floating-point, max length for string, minimum length
                            for integer
                    l       interpret integer as C type "long" or "unsigned long"
                    h       interpret integer as C type "short" or "unsigned short"
                            If no flags, interpret integer as C type "int" or "unsigned"
    
                 There are also two Perl-specific flags:
    
                    V       interpret integer as Perl's standard integer type
                    v       interpret string as a vector of integers, output as
                            numbers separated either by dots, or by an arbitrary
                            string received from the argument list when the flag
                            is preceded by C<*>
    
                 Where a number would appear in the flags, an
                 asterisk (`*') may be used instead, in which case
                 Perl uses the next item in the parameter list as the
                 given number (that is, as the field width or
                 precision).  If a field width obtained through `*'
                 is negative, it has the same effect as the `-' flag:
                 left-justification.
                 The `v' flag is useful for displaying ordinal values
                 of characters in arbitrary strings:
    
                     printf "version is v%vd\n", $^V;            # Perl's version
                     printf "address is %*vX\n", ":", $addr;     # IPv6 address
                     printf "bits are %*vb\n", " ", $bits;       # random bitstring
    
                 If `use locale' is in effect, the character used for
                 the decimal point in formatted real numbers is
                 affected by the LC_NUMERIC locale.  See the
                 perllocale manpage.
    
                 If Perl understands "quads" (64-bit integers) (this
                 requires either that the platform natively support
                 quads or that Perl be specifically compiled to
                 support quads), the characters
    
                         d u o x X b i D U O
    
                 print quads, and they may optionally be preceded by
    
                         ll L q
    
                 For example
    
                         %lld %16LX %qo
    
                 You can find out whether your Perl supports quads
                 via the Config manpage:
    
                         use Config;
                         ($Config{use64bitint} eq 'define' || $Config{longsize} == 8) &&
                                 print "quads\n";
    
                 If Perl understands "long doubles" (this requires
                 that the platform support long doubles), the flags
    
                         e f g E F G
    
                 may optionally be preceded by
    
                         ll L
    
                 For example
    
                         %llf %Lg
    
                 You can find out whether your Perl supports long
                 doubles via the Config manpage:
    
                         use Config;
                         $Config{d_longdbl} eq 'define' && print "long doubles\n";
    
         sqrt EXPR
    
         sqrt    Return the square root of EXPR.  If EXPR is omitted,
                 returns square root of `$_'.  Only works on non-
                 negative operands, unless you've loaded the standard
                 Math::Complex module.
    
                     use Math::Complex;
                     print sqrt(-2);    # prints 1.4142135623731i
    
    
         srand EXPR
    
         srand   Sets the random number seed for the `rand' operator.
                 If EXPR is omitted, uses a semi-random value
                 supplied by the kernel (if it supports the
                 /dev/urandom device) or based on the current time
                 and process ID, among other things.  In versions of
                 Perl prior to 5.004 the default seed was just the
                 current `time'.  This isn't a particularly good
                 seed, so many old programs supply their own seed
                 value (often `time ^ $$' or `time ^ ($$ + ($$ <<
                 15))'), but that isn't necessary any more.
    
                 In fact, it's usually not necessary to call `srand'
                 at all, because if it is not called explicitly, it
                 is called implicitly at the first use of the `rand'
                 operator.  However, this was not the case in version
                 of Perl before 5.004, so if your script will run
                 under older Perl versions, it should call `srand'.
    
                 Note that you need something much more random than
                 the default seed for cryptographic purposes.
                 Checksumming the compressed output of one or more
                 rapidly changing operating system status programs is
                 the usual method.  For example:
    
                     srand (time ^ $$ ^ unpack "%L*", `ps axww | gzip`);
    
                 If you're particularly concerned with this, see the
                 `Math::TrulyRandom' module in CPAN.
    
                 Do not call `srand' multiple times in your program
                 unless you know exactly what you're doing and why
                 you're doing it.  The point of the function is to
                 "seed" the `rand' function so that `rand' can
                 produce a different sequence each time you run your
                 program.  Just do it once at the top of your
                 program, or you won't get random numbers out of
                 `rand'!
    
                 Frequently called programs (like CGI scripts) that
                 simply use
    
                     time ^ $$
    
                 for a seed can fall prey to the mathematical
                 property that
    
                     a^b == (a+1)^(b+1)
    
                 one-third of the time.  So don't do that.
    
         stat FILEHANDLE
    
         stat EXPR
    
         stat    Returns a 13-element list giving the status info for
                 a file, either the file opened via FILEHANDLE, or
                 named by EXPR.  If EXPR is omitted, it stats `$_'.
                 Returns a null list if the stat fails.  Typically
                 used as follows:
    
                     ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
                        $atime,$mtime,$ctime,$blksize,$blocks)
                            = stat($filename);
    
                 Not all fields are supported on all filesystem
                 types.  Here are the meaning of the fields:
    
                   0 dev      device number of filesystem
                   1 ino      inode number
                   2 mode     file mode  (type and permissions)
                   3 nlink    number of (hard) links to the file
                   4 uid      numeric user ID of file's owner
                   5 gid      numeric group ID of file's owner
                   6 rdev     the device identifier (special files only)
                   7 size     total size of file, in bytes
                   8 atime    last access time in seconds since the epoch
                   9 mtime    last modify time in seconds since the epoch
                  10 ctime    inode change time (NOT creation time!) in seconds since the epoch
                  11 blksize  preferred block size for file system I/O
                  12 blocks   actual number of blocks allocated
    
                 (The epoch was at 00:00 January 1, 1970 GMT.)
    
                 If stat is passed the special filehandle consisting
                 of an underline, no stat is done, but the current
                 contents of the stat structure from the last stat or
                 filetest are returned.  Example:
    
                     if (-x $file && (($d) = stat(_)) && $d < 0) {
                         print "$file is executable NFS file\n";
                     }
    
                 (This works on machines only for which the device
                 number is negative under NFS.)
    
                 Because the mode contains both the file type and its
                 permissions, you should mask off the file type
                 portion and (s)printf using a `"%o"' if you want to
                 see the real permissions.
    
                     $mode = (stat($filename))[2];
                     printf "Permissions are %04o\n", $mode & 07777;
    
                 In scalar context, `stat' returns a boolean value
                 indicating success or failure, and, if successful,
                 sets the information associated with the special
                 filehandle `_'.
    
                 The File::stat module provides a convenient, by-name
                 access mechanism:
    
                     use File::stat;
                     $sb = stat($filename);
                     printf "File is %s, size is %s, perm %04o, mtime %s\n",
                         $filename, $sb->size, $sb->mode & 07777,
                         scalar localtime $sb->mtime;
    
                 You can import symbolic mode constants (`S_IF*') and
                 functions (`S_IS*') from the Fcntl module:
    
                     use Fcntl ':mode';
    
                     $mode = (stat($filename))[2];
    
                     $user_rwx      = ($mode & S_IRWXU) >> 6;
                     $group_read    = ($mode & S_IRGRP) >> 3;
                     $other_execute =  $mode & S_IXOTH;
    
                     printf "Permissions are %04o\n", S_ISMODE($mode), "\n";
    
                     $is_setuid     =  $mode & S_ISUID;
                     $is_setgid     =  S_ISDIR($mode);
    
                 You could write the last two using the `-u' and `-d'
                 operators.  The commonly available S_IF* constants
                 are
    
                     # Permissions: read, write, execute, for user, group, others.
    
                     S_IRWXU S_IRUSR S_IWUSR S_IXUSR
                     S_IRWXG S_IRGRP S_IWGRP S_IXGRP
                     S_IRWXO S_IROTH S_IWOTH S_IXOTH
    
                     # Setuid/Setgid/Stickiness.
                     S_ISUID S_ISGID S_ISVTX S_ISTXT
    
                     # File types.  Not necessarily all are available on your system.
    
                     S_IFREG S_IFDIR S_IFLNK S_IFBLK S_ISCHR S_IFIFO S_IFSOCK S_IFWHT S_ENFMT
    
                     # The following are compatibility aliases for S_IRUSR, S_IWUSR, S_IXUSR.
    
                     S_IREAD S_IWRITE S_IEXEC
    
                 and the S_IF* functions are
    
                     S_IFMODE($mode)     the part of $mode containg the permission bits
                                         and the setuid/setgid/sticky bits
    
                     S_IFMT($mode)       the part of $mode containing the file type
                                         which can be bit-anded with e.g. S_IFREG
                                         or with the following functions
    
                     # The operators -f, -d, -l, -b, -c, -p, and -s.
    
                     S_ISREG($mode) S_ISDIR($mode) S_ISLNK($mode)
                     S_ISBLK($mode) S_ISCHR($mode) S_ISFIFO($mode) S_ISSOCK($mode)
    
                     # No direct -X operator counterpart, but for the first one
                     # the -g operator is often equivalent.  The ENFMT stands for
                     # record flocking enforcement, a platform-dependent feature.
    
                     S_ISENFMT($mode) S_ISWHT($mode)
    
                 See your native chmod(2) and stat(2) documentation
                 for more details about the S_* constants.
    
         study SCALAR
    
         study   Takes extra time to study SCALAR (`$_' if
                 unspecified) in anticipation of doing many pattern
                 matches on the string before it is next modified.
                 This may or may not save time, depending on the
                 nature and number of patterns you are searching on,
                 and on the distribution of character frequencies in
                 the string to be searched--you probably want to
                 compare run times with and without it to see which
                 runs faster.  Those loops which scan for many short
                 constant strings (including the constant parts of
                 more complex patterns) will benefit most.  You may
                 have only one `study' active at a time--if you study
                 a different scalar the first is "unstudied".  (The
                 way `study' works is this: a linked list of every
                 character in the string to be searched is made, so
                 we know, for example, where all the `'k'' characters
                 are.  From each search string, the rarest character
                 is selected, based on some static frequency tables
                 constructed from some C programs and English text.
                 Only those places that contain this "rarest"
                 character are examined.)
    
                 For example, here is a loop that inserts index
                 producing entries before any line containing a
                 certain pattern:
    
                     while (<>) {
                         study;
                         print ".IX foo\n"       if /\bfoo\b/;
                         print ".IX bar\n"       if /\bbar\b/;
                         print ".IX blurfl\n"    if /\bblurfl\b/;
                         # ...
                         print;
                     }
    
                 In searching for `/\bfoo\b/', only those locations
                 in `$_' that contain `f' will be looked at, because
                 `f' is rarer than `o'.  In general, this is a big
                 win except in pathological cases.  The only question
                 is whether it saves you more time than it took to
                 build the linked list in the first place.
    
                 Note that if you have to look for strings that you
                 don't know till runtime, you can build an entire
                 loop as a string and `eval' that to avoid
                 recompiling all your patterns all the time.
                 Together with undefining `$/' to input entire files
                 as one record, this can be very fast, often faster
                 than specialized programs like fgrep(1).  The
                 following scans a list of files (`@files') for a
                 list of words (`@words'), and prints out the names
                 of those files that contain a match:
    
                     $search = 'while (<>) { study;';
                     foreach $word (@words) {
                         $search .= "++\$seen{\$ARGV} if /\\b$word\\b/;\n";
                     }
                     $search .= "}";
                     @ARGV = @files;
                     undef $/;
                     eval $search;               # this screams
                     $/ = "\n";          # put back to normal input delimiter
                     foreach $file (sort keys(%seen)) {
                         print $file, "\n";
                     }
    
    
         sub BLOCK
    
         sub NAME
    
         sub NAME BLOCK
                 This is subroutine definition, not a real function
                 per se.  With just a NAME (and possibly prototypes
                 or attributes), it's just a forward declaration.
                 Without a NAME, it's an anonymous function
                 declaration, and does actually return a value: the
                 CODE ref of the closure you just created.  See the
                 perlsub manpage and the perlref manpage for details.
    
         substr EXPR,OFFSET,LENGTH,REPLACEMENT
    
         substr EXPR,OFFSET,LENGTH
    
         substr EXPR,OFFSET
                 Extracts a substring out of EXPR and returns it.
                 First character is at offset `0', or whatever you've
                 set `$[' to (but don't do that).  If OFFSET is
                 negative (or more precisely, less than `$['), starts
                 that far from the end of the string.  If LENGTH is
                 omitted, returns everything to the end of the
                 string.  If LENGTH is negative, leaves that many
                 characters off the end of the string.
    
                 You can use the substr() function as an lvalue, in
                 which case EXPR must itself be an lvalue.  If you
                 assign something shorter than LENGTH, the string
                 will shrink, and if you assign something longer than
                 LENGTH, the string will grow to accommodate it.  To
                 keep the string the same length you may need to pad
                 or chop your value using `sprintf'.
    
                 If OFFSET and LENGTH specify a substring that is
                 partly outside the string, only the part within the
                 string is returned.  If the substring is beyond
                 either end of the string, substr() returns the
                 undefined value and produces a warning.  When used
                 as an lvalue, specifying a substring that is
                 entirely outside the string is a fatal error.
                 Here's an example showing the behavior for boundary
                 cases:
    
                     my $name = 'fred';
                     substr($name, 4) = 'dy';            # $name is now 'freddy'
                     my $null = substr $name, 6, 2;      # returns '' (no warning)
                     my $oops = substr $name, 7;         # returns undef, with warning
                     substr($name, 7) = 'gap';           # fatal error
    
                 An alternative to using substr() as an lvalue is to
                 specify the replacement string as the 4th argument.
                 This allows you to replace parts of the EXPR and
                 return what was there before in one operation, just
                 as you can with splice().
    
         symlink OLDFILE,NEWFILE
                 Creates a new filename symbolically linked to the
                 old filename.  Returns `1' for success, `0'
                 otherwise.  On systems that don't support symbolic
                 links, produces a fatal error at run time.  To check
                 for that, use eval:
    
                     $symlink_exists = eval { symlink("",""); 1 };
    
    
         syscall LIST
                 Calls the system call specified as the first element
                 of the list, passing the remaining elements as
                 arguments to the system call.  If unimplemented,
                 produces a fatal error.  The arguments are
                 interpreted as follows: if a given argument is
                 numeric, the argument is passed as an int.  If not,
                 the pointer to the string value is passed.  You are
                 responsible to make sure a string is pre-extended
                 long enough to receive any result that might be
                 written into a string.  You can't use a string
                 literal (or other read-only string) as an argument
                 to `syscall' because Perl has to assume that any
                 string pointer might be written through.  If your
                 integer arguments are not literals and have never
                 been interpreted in a numeric context, you may need
                 to add `0' to them to force them to look like
                 numbers.  This emulates the `syswrite' function (or
                 vice versa):
    
                     require 'syscall.ph';               # may need to run h2ph
                     $s = "hi there\n";
                     syscall(&SYS_write, fileno(STDOUT), $s, length $s);
    
                 Note that Perl supports passing of up to only 14
                 arguments to your system call, which in practice
                 should usually suffice.
    
                 Syscall returns whatever value returned by the
                 system call it calls.  If the system call fails,
                 `syscall' returns `-1' and sets `$!' (errno).  Note
                 that some system calls can legitimately return `-1'.
                 The proper way to handle such calls is to assign
                 `$!=0;' before the call and check the value of `$!'
                 if syscall returns `-1'.
    
                 There's a problem with `syscall(&SYS_pipe)': it
                 returns the file number of the read end of the pipe
                 it creates.  There is no way to retrieve the file
                 number of the other end.  You can avoid this problem
                 by using `pipe' instead.
    
         sysopen FILEHANDLE,FILENAME,MODE
    
         sysopen FILEHANDLE,FILENAME,MODE,PERMS
                 Opens the file whose filename is given by FILENAME,
                 and associates it with FILEHANDLE.  If FILEHANDLE is
                 an expression, its value is used as the name of the
                 real filehandle wanted.  This function calls the
                 underlying operating system's `open' function with
                 the parameters FILENAME, MODE, PERMS.
    
                 The possible values and flag bits of the MODE
                 parameter are system-dependent; they are available
                 via the standard module `Fcntl'.  See the
                 documentation of your operating system's `open' to
                 see which values and flag bits are available.  You
                 may combine several flags using the `|'-operator.
    
                 Some of the most common values are `O_RDONLY' for
                 opening the file in read-only mode, `O_WRONLY' for
                 opening the file in write-only mode, and `O_RDWR'
                 for opening the file in read-write mode, and.
    
                 For historical reasons, some values work on almost
                 every system supported by perl: zero means read-
                 only, one means write-only, and two means
                 read/write.  We know that these values do not work
                 under OS/390 & VM/ESA Unix and on the Macintosh; you
                 probably don't want to use them in new code.
    
                 If the file named by FILENAME does not exist and the
                 `open' call creates it (typically because MODE
                 includes the `O_CREAT' flag), then the value of
                 PERMS specifies the permissions of the newly created
                 file.  If you omit the PERMS argument to `sysopen',
                 Perl uses the octal value `0666'.  These permission
                 values need to be in octal, and are modified by your
                 process's current `umask'.
    
                 In many systems the `O_EXCL' flag is available for
                 opening files in exclusive mode.  This is not
                 locking: exclusiveness means here that if the file
                 already exists, sysopen() fails.  The `O_EXCL' wins
                 `O_TRUNC'.
    
                 Sometimes you may want to truncate an already-
                 existing file: `O_TRUNC'.
    
                 You should seldom if ever use `0644' as argument to
                 `sysopen', because that takes away the user's option
                 to have a more permissive umask.  Better to omit it.
                 See the perlfunc(1) entry on `umask' for more on
                 this.
    
                 Note that `sysopen' depends on the fdopen() C
                 library function.  On many UNIX systems, fdopen() is
                 known to fail when file descriptors exceed a certain
                 value, typically 255. If you need more file
                 descriptors than that, consider rebuilding Perl to
                 use the `sfio' library, or perhaps using the
                 POSIX:\fIs0:open() function.
    
                 See the perlopentut manpage for a kinder, gentler
                 explanation of opening files.
    
         sysread FILEHANDLE,SCALAR,LENGTH,OFFSET
    
         sysread FILEHANDLE,SCALAR,LENGTH
                 Attempts to read LENGTH bytes of data into variable
                 SCALAR from the specified FILEHANDLE, using the
                 system call read(2).  It bypasses stdio, so mixing
                 this with other kinds of reads, `print', `write',
                 `seek', `tell', or `eof' can cause confusion because
                 stdio usually buffers data.  Returns the number of
                 bytes actually read, `0' at end of file, or undef if
                 there was an error.  SCALAR will be grown or shrunk
                 so that the last byte actually read is the last byte
                 of the scalar after the read.
    
                 An OFFSET may be specified to place the read data at
                 some place in the string other than the beginning.
                 A negative OFFSET specifies placement at that many
                 bytes counting backwards from the end of the string.
                 A positive OFFSET greater than the length of SCALAR
                 results in the string being padded to the required
                 size with `"\0"' bytes before the result of the read
                 is appended.
    
                 There is no syseof() function, which is ok, since
                 eof() doesn't work very well on device files (like
                 ttys) anyway.  Use sysread() and check for a return
                 value for 0 to decide whether you're done.
    
         sysseek FILEHANDLE,POSITION,WHENCE
                 Sets FILEHANDLE's system position using the system
                 call lseek(2).  It bypasses stdio, so mixing this
                 with reads (other than `sysread'), `print', `write',
                 `seek', `tell', or `eof' may cause confusion.
                 FILEHANDLE may be an expression whose value gives
                 the name of the filehandle.  The values for WHENCE
                 are `0' to set the new position to POSITION, `1' to
                 set the it to the current position plus POSITION,
                 and `2' to set it to EOF plus POSITION (typically
                 negative).  For WHENCE, you may also use the
                 constants `SEEK_SET', `SEEK_CUR', and `SEEK_END'
                 (start of the file, current position, end of the
                 file) from the Fcntl module.
    
                 Returns the new position, or the undefined value on
                 failure.  A position of zero is returned as the
                 string `"0 but true"'; thus `sysseek' returns true
                 on success and false on failure, yet you can still
                 easily determine the new position.
    
         system LIST
    
         system PROGRAM LIST
                 Does exactly the same thing as `exec LIST', except
                 that a fork is done first, and the parent process
                 waits for the child process to complete.  Note that
                 argument processing varies depending on the number
                 of arguments.  If there is more than one argument in
                 LIST, or if LIST is an array with more than one
                 value, starts the program given by the first element
                 of the list with arguments given by the rest of the
                 list.  If there is only one scalar argument, the
                 argument is checked for shell metacharacters, and if
                 there are any, the entire argument is passed to the
                 system's command shell for parsing (this is `/bin/sh
                 -c' on Unix platforms, but varies on other
                 platforms).  If there are no shell metacharacters in
                 the argument, it is split into words and passed
                 directly to `execvp', which is more efficient.
    
                 Beginning with v5.6.0, Perl will attempt to flush
                 all files opened for output before any operation
                 that may do a fork, but this may not be supported on
                 some platforms (see the perlport manpage).  To be
                 safe, you may need to set `$|' ($AUTOFLUSH in
                 English) or call the `autoflush()' method of
                 `IO::Handle' on any open handles.
    
                 The return value is the exit status of the program
                 as returned by the `wait' call.  To get the actual
                 exit value divide by 256.  See also the exec entry
                 elsewhere in this document.  This is not what you
                 want to use to capture the output from a command,
                 for that you should use merely backticks or `qx//',
                 as described in the section on "`STRING`" in the
                 perlop manpage.  Return value of -1 indicates a
                 failure to start the program (inspect $! for the
                 reason).
    
                 Like `exec', `system' allows you to lie to a program
                 about its name if you use the `system PROGRAM LIST'
                 syntax.  Again, see the exec entry elsewhere in this
                 document.
    
                 Because `system' and backticks block `SIGINT' and
                 `SIGQUIT', killing the program they're running
                 doesn't actually interrupt your program.
    
                     @args = ("command", "arg1", "arg2");
                     system(@args) == 0
                          or die "system @args failed: $?"
    
                 You can check all the failure possibilities by
                 inspecting `$?' like this:
    
                     $exit_value  = $? >> 8;
                     $signal_num  = $? & 127;
                     $dumped_core = $? & 128;
    
                 When the arguments get executed via the system
                 shell, results and return codes will be subject to
                 its quirks and capabilities.  See the section on
                 "`STRING`" in the perlop manpage and the exec entry
                 elsewhere in this document for details.
    
         syswrite FILEHANDLE,SCALAR,LENGTH,OFFSET
    
         syswrite FILEHANDLE,SCALAR,LENGTH
    
         syswrite FILEHANDLE,SCALAR
                 Attempts to write LENGTH bytes of data from variable
                 SCALAR to the specified FILEHANDLE, using the system
                 call write(2).  If LENGTH is not specified, writes
                 whole SCALAR.  It bypasses stdio, so mixing this
                 with reads (other than `sysread())', `print',
                 `write', `seek', `tell', or `eof' may cause
                 confusion because stdio usually buffers data.
                 Returns the number of bytes actually written, or
                 `undef' if there was an error.  If the LENGTH is
                 greater than the available data in the SCALAR after
                 the OFFSET, only as much data as is available will
                 be written.
    
                 An OFFSET may be specified to write the data from
                 some part of the string other than the beginning.  A
                 negative OFFSET specifies writing that many bytes
                 counting backwards from the end of the string.  In
                 the case the SCALAR is empty you can use OFFSET but
                 only zero offset.
    
         tell FILEHANDLE
    
         tell    Returns the current position for FILEHANDLE.
                 FILEHANDLE may be an expression whose value gives
                 the name of the actual filehandle.  If FILEHANDLE is
                 omitted, assumes the file last read.
    
                 There is no `systell' function.  Use `sysseek(FH, 0,
                 1)' for that.
    
         telldir DIRHANDLE
                 Returns the current position of the `readdir'
                 routines on DIRHANDLE.  Value may be given to
                 `seekdir' to access a particular location in a
                 directory.  Has the same caveats about possible
                 directory compaction as the corresponding system
                 library routine.
    
         tie VARIABLE,CLASSNAME,LIST
                 This function binds a variable to a package class
                 that will provide the implementation for the
                 variable.  VARIABLE is the name of the variable to
                 be enchanted.  CLASSNAME is the name of a class
                 implementing objects of correct type.  Any
                 additional arguments are passed to the `new' method
                 of the class (meaning `TIESCALAR', `TIEHANDLE',
                 `TIEARRAY', or `TIEHASH').  Typically these are
                 arguments such as might be passed to the
                 `dbm_open()' function of C.  The object returned by
                 the `new' method is also returned by the `tie'
                 function, which would be useful if you want to
                 access other methods in CLASSNAME.
    
                 Note that functions such as `keys' and `values' may
                 return huge lists when used on large objects, like
                 DBM files.  You may prefer to use the `each'
                 function to iterate over such.  Example:
    
                     # print out history file offsets
                     use NDBM_File;
                     tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);
                     while (($key,$val) = each %HIST) {
                         print $key, ' = ', unpack('L',$val), "\n";
                     }
                     untie(%HIST);
    
                 A class implementing a hash should have the
                 following methods:
    
    
    
                     TIEHASH classname, LIST
                     FETCH this, key
                     STORE this, key, value
                     DELETE this, key
                     CLEAR this
                     EXISTS this, key
                     FIRSTKEY this
                     NEXTKEY this, lastkey
                     DESTROY this
    
                 A class implementing an ordinary array should have
                 the following methods:
    
                     TIEARRAY classname, LIST
                     FETCH this, key
                     STORE this, key, value
                     FETCHSIZE this
                     STORESIZE this, count
                     CLEAR this
                     PUSH this, LIST
                     POP this
                     SHIFT this
                     UNSHIFT this, LIST
                     SPLICE this, offset, length, LIST
                     EXTEND this, count
                     DESTROY this
    
                 A class implementing a file handle should have the
                 following methods:
    
                     TIEHANDLE classname, LIST
                     READ this, scalar, length, offset
                     READLINE this
                     GETC this
                     WRITE this, scalar, length, offset
                     PRINT this, LIST
                     PRINTF this, format, LIST
                     CLOSE this
                     DESTROY this
    
                 A class implementing a scalar should have the
                 following methods:
    
                     TIESCALAR classname, LIST
                     FETCH this,
                     STORE this, value
                     DESTROY this
    
                 Not all methods indicated above need be implemented.
                 See the perltie manpage, the Tie::Hash manpage, the
                 Tie::Array manpage, the Tie::Scalar manpage, and the
                 Tie::Handle manpage.
                 Unlike `dbmopen', the `tie' function will not use or
                 require a module for you--you need to do that
                 explicitly yourself.  See the DB_File manpage or the
                 Config module for interesting `tie' implementations.
    
                 For further details see the perltie manpage, the
                 section on "tied VARIABLE".
    
         tied VARIABLE
                 Returns a reference to the object underlying
                 VARIABLE (the same value that was originally
                 returned by the `tie' call that bound the variable
                 to a package.)  Returns the undefined value if
                 VARIABLE isn't tied to a package.
    
         time    Returns the number of non-leap seconds since
                 whatever time the system considers to be the epoch
                 (that's 00:00:00, January 1, 1904 for MacOS, and
                 00:00:00 UTC, January 1, 1970 for most other
                 systems).  Suitable for feeding to `gmtime' and
                 `localtime'.
    
                 For measuring time in better granularity than one
                 second, you may use either the Time::HiRes module
                 from CPAN, or if you have gettimeofday(2), you may
                 be able to use the `syscall' interface of Perl, see
                 the perlfaq8 manpage for details.
    
         times   Returns a four-element list giving the user and
                 system times, in seconds, for this process and the
                 children of this process.
    
                     ($user,$system,$cuser,$csystem) = times;
    
    
         tr///   The transliteration operator.  Same as `y///'.  See
                 the perlop manpage.
    
         truncate FILEHANDLE,LENGTH
    
         truncate EXPR,LENGTH
                 Truncates the file opened on FILEHANDLE, or named by
                 EXPR, to the specified length.  Produces a fatal
                 error if truncate isn't implemented on your system.
                 Returns true if successful, the undefined value
                 otherwise.
    
         uc EXPR
    
         uc      Returns an uppercased version of EXPR.  This is the
                 internal function implementing the `\U' escape in
                 double-quoted strings.  Respects current LC_CTYPE
                 locale if `use locale' in force.  See the perllocale
                 manpage.  Under Unicode (`use utf8') it uses the
                 standard Unicode uppercase mappings.  (It does not
                 attempt to do titlecase mapping on initial letters.
                 See `ucfirst' for that.)
    
                 If EXPR is omitted, uses `$_'.
    
         ucfirst EXPR
    
         ucfirst Returns the value of EXPR with the first character
                 in uppercase (titlecase in Unicode).  This is the
                 internal function implementing the `\u' escape in
                 double-quoted strings.  Respects current LC_CTYPE
                 locale if `use locale' in force.  See the perllocale
                 manpage and the utf8 manpage.
    
                 If EXPR is omitted, uses `$_'.
    
         umask EXPR
    
         umask   Sets the umask for the process to EXPR and returns
                 the previous value.  If EXPR is omitted, merely
                 returns the current umask.
    
                 The Unix permission `rwxr-x---' is represented as
                 three sets of three bits, or three octal digits:
                 `0750' (the leading 0 indicates octal and isn't one
                 of the digits).  The `umask' value is such a number
                 representing disabled permissions bits.  The
                 permission (or "mode") values you pass `mkdir' or
                 `sysopen' are modified by your umask, so even if you
                 tell `sysopen' to create a file with permissions
                 `0777', if your umask is `0022' then the file will
                 actually be created with permissions `0755'.  If
                 your `umask' were `0027' (group can't write; others
                 can't read, write, or execute), then passing
                 `sysopen' `0666' would create a file with mode
                 `0640' (`0666 &~ 027' is `0640').
    
                 Here's some advice: supply a creation mode of `0666'
                 for regular files (in `sysopen') and one of `0777'
                 for directories (in `mkdir') and executable files.
                 This gives users the freedom of choice: if they want
                 protected files, they might choose process umasks of
                 `022', `027', or even the particularly antisocial
                 mask of `077'.  Programs should rarely if ever make
                 policy decisions better left to the user.  The
                 exception to this is when writing files that should
                 be kept private: mail files, web browser cookies,
                 .rhosts files, and so on.
    
                 If umask(2) is not implemented on your system and
                 you are trying to restrict access for yourself
                 (i.e., (EXPR & 0700) > 0), produces a fatal error at
                 run time.  If umask(2) is not implemented and you
                 are not trying to restrict access for yourself,
                 returns `undef'.
    
                 Remember that a umask is a number, usually given in
                 octal; it is not a string of octal digits.  See also
                 the oct entry elsewhere in this document, if all you
                 have is a string.
    
         undef EXPR
    
         undef   Undefines the value of EXPR, which must be an
                 lvalue.  Use only on a scalar value, an array (using
                 `@'), a hash (using `%'), a subroutine (using `&'),
                 or a typeglob (using <*>).  (Saying `undef
                 $hash{$key}' will probably not do what you expect on
                 most predefined variables or DBM list values, so
                 don't do that; see the delete manpage.)  Always
                 returns the undefined value.  You can omit the EXPR,
                 in which case nothing is undefined, but you still
                 get an undefined value that you could, for instance,
                 return from a subroutine, assign to a variable or
                 pass as a parameter.  Examples:
    
                     undef $foo;
                     undef $bar{'blurfl'};      # Compare to: delete $bar{'blurfl'};
                     undef @ary;
                     undef %hash;
                     undef &mysub;
                     undef *xyz;       # destroys $xyz, @xyz, %xyz, &xyz, etc.
                     return (wantarray ? (undef, $errmsg) : undef) if $they_blew_it;
                     select undef, undef, undef, 0.25;
                     ($a, $b, undef, $c) = &foo;       # Ignore third value returned
    
                 Note that this is a unary operator, not a list
                 operator.
    
         unlink LIST
    
         unlink  Deletes a list of files.  Returns the number of
                 files successfully deleted.
    
                     $cnt = unlink 'a', 'b', 'c';
                     unlink @goners;
                     unlink <*.bak>;
    
                 Note: `unlink' will not delete directories unless
                 you are superuser and the -U flag is supplied to
                 Perl.  Even if these conditions are met, be warned
                 that unlinking a directory can inflict damage on
                 your filesystem.  Use `rmdir' instead.
    
                 If LIST is omitted, uses `$_'.
    
         unpack TEMPLATE,EXPR
                 `unpack' does the reverse of `pack': it takes a
                 string and expands it out into a list of values.
                 (In scalar context, it returns merely the first
                 value produced.)
    
                 The string is broken into chunks described by the
                 TEMPLATE.  Each chunk is converted separately to a
                 value.  Typically, either the string is a result of
                 `pack', or the bytes of the string represent a C
                 structure of some kind.
    
                 The TEMPLATE has the same format as in the `pack'
                 function.  Here's a subroutine that does substring:
    
                     sub substr {
                         my($what,$where,$howmuch) = @_;
                         unpack("x$where a$howmuch", $what);
                     }
    
                 and then there's
    
                     sub ordinal { unpack("c",$_[0]); } # same as ord()
    
                 In addition to fields allowed in pack(), you may
                 prefix a field with a %<number> to indicate that you
                 want a <number>-bit checksum of the items instead of
                 the items themselves.  Default is a 16-bit checksum.
                 Checksum is calculated by summing numeric values of
                 expanded values (for string fields the sum of
                 `ord($char)' is taken, for bit fields the sum of
                 zeroes and ones).
    
                 For example, the following computes the same number
                 as the System V sum program:
    
                     $checksum = do {
                         local $/;  # slurp!
                         unpack("%32C*",<>) % 65535;
                     };
    
                 The following efficiently counts the number of set
                 bits in a bit vector:
    
                     $setbits = unpack("%32b*", $selectmask);
    
                 The `p' and `P' formats should be used with care.
                 Since Perl has no way of checking whether the value
                 passed to `unpack()' corresponds to a valid memory
                 location, passing a pointer value that's not known
                 to be valid is likely to have disastrous
                 consequences.
    
                 If the repeat count of a field is larger than what
                 the remainder of the input string allows, repeat
                 count is decreased.  If the input string is longer
                 than one described by the TEMPLATE, the rest is
                 ignored.
    
                 See the pack entry elsewhere in this document for
                 more examples and notes.
    
         untie VARIABLE
                 Breaks the binding between a variable and a package.
                 (See `tie'.)
    
         unshift ARRAY,LIST
                 Does the opposite of a `shift'.  Or the opposite of
                 a `push', depending on how you look at it.  Prepends
                 list to the front of the array, and returns the new
                 number of elements in the array.
    
                     unshift(ARGV, '-e') unless $ARGV[0] =~ /^-/;
    
                 Note the LIST is prepended whole, not one element at
                 a time, so the prepended elements stay in the same
                 order.  Use `reverse' to do the reverse.
    
         use Module VERSION LIST
    
         use Module VERSION
    
         use Module LIST
    
         use Module
    
         use VERSION
                 Imports some semantics into the current package from
                 the named module, generally by aliasing certain
                 subroutine or variable names into your package.  It
                 is exactly equivalent to
    
                     BEGIN { require Module; import Module LIST; }
    
                 except that Module must be a bareword.
    
                 VERSION, which can be specified as a literal of the
                 form v5.6.1, demands that the current version of
                 Perl (`$^V' or $PERL_VERSION) be at least as recent
                 as that version.  (For compatibility with older
                 versions of Perl, a numeric literal will also be
                 interpreted as VERSION.)  If the version of the
                 running Perl interpreter is less than VERSION, then
                 an error message is printed and Perl exits
                 immediately without attempting to parse the rest of
                 the file.  Compare with the require entry elsewhere
                 in this document, which can do a similar check at
                 run time.
    
                     use v5.6.1;         # compile time version check
                     use 5.6.1;          # ditto
                     use 5.005_03;       # float version allowed for compatibility
    
                 This is often useful if you need to check the
                 current Perl version before `use'ing library modules
                 that have changed in incompatible ways from older
                 versions of Perl.  (We try not to do this more than
                 we have to.)
    
                 The `BEGIN' forces the `require' and `import' to
                 happen at compile time.  The `require' makes sure
                 the module is loaded into memory if it hasn't been
                 yet.  The `import' is not a builtin--it's just an
                 ordinary static method call into the `Module'
                 package to tell the module to import the list of
                 features back into the current package.  The module
                 can implement its `import' method any way it likes,
                 though most modules just choose to derive their
                 `import' method via inheritance from the `Exporter'
                 class that is defined in the `Exporter' module.  See
                 the Exporter manpage.  If no `import' method can be
                 found then the call is skipped.
    
                 If you don't want your namespace altered, explicitly
                 supply an empty list:
    
                     use Module ();
    
                 That is exactly equivalent to
    
                     BEGIN { require Module }
    
                 If the VERSION argument is present between Module
                 and LIST, then the `use' will call the VERSION
                 method in class Module with the given version as an
                 argument.  The default VERSION method, inherited
                 from the UNIVERSAL class, croaks if the given
                 version is larger than the value of the variable
                 `$Module::VERSION'.
    
                 Again, there is a distinction between omitting LIST
                 (`import' called with no arguments) and an explicit
                 empty LIST `()' (`import' not called).  Note that
                 there is no comma after VERSION!
    
                 Because this is a wide-open interface, pragmas
                 (compiler directives) are also implemented this way.
                 Currently implemented pragmas are:
    
                     use integer;
                     use diagnostics;
                     use sigtrap  qw(SEGV BUS);
                     use strict   qw(subs vars refs);
                     use subs     qw(afunc blurfl);
                     use warnings qw(all);
    
                 Some of these pseudo-modules import semantics into
                 the current block scope (like `strict' or `integer',
                 unlike ordinary modules, which import symbols into
                 the current package (which are effective through the
                 end of the file).
    
                 There's a corresponding `no' command that unimports
                 meanings imported by `use', i.e., it calls `unimport
                 Module LIST' instead of `import'.
    
                     no integer;
                     no strict 'refs';
                     no warnings;
    
                 If no `unimport' method can be found the call fails
                 with a fatal error.
    
                 See the perlmod manpage for a list of standard
                 modules and pragmas.
    
         utime LIST
                 Changes the access and modification times on each
                 file of a list of files.  The first two elements of
                 the list must be the NUMERICAL access and
                 modification times, in that order.  Returns the
                 number of files successfully changed.  The inode
                 change time of each file is set to the current time.
                 This code has the same effect as the `touch' command
                 if the files already exist:
    
                     #!/usr/bin/perl
                     $now = time;
                     utime $now, $now, @ARGV;
    
    
         values HASH
                 Returns a list consisting of all the values of the
                 named hash.  (In a scalar context, returns the
                 number of values.)  The values are returned in an
                 apparently random order.  The actual random order is
                 subject to change in future versions of perl, but it
                 is guaranteed to be the same order as either the
                 `keys' or `each' function would produce on the same
                 (unmodified) hash.
    
                 Note that you cannot modify the values of a hash
                 this way, because the returned list is just a copy.
                 You need to use a hash slice for that, since it's
                 lvaluable in a way that values() is not.
    
                     for (values %hash)      { s/foo/bar/g }   # FAILS!
                     for (@hash{keys %hash}) { s/foo/bar/g }   # ok
    
                 As a side effect, calling values() resets the HASH's
                 internal iterator.  See also `keys', `each', and
                 `sort'.
    
         vec EXPR,OFFSET,BITS
                 Treats the string in EXPR as a bit vector made up of
                 elements of width BITS, and returns the value of the
                 element specified by OFFSET as an unsigned integer.
                 BITS therefore specifies the number of bits that are
                 reserved for each element in the bit vector.  This
                 must be a power of two from 1 to 32 (or 64, if your
                 platform supports that).
    
                 If BITS is 8, "elements" coincide with bytes of the
                 input string.
    
                 If BITS is 16 or more, bytes of the input string are
                 grouped into chunks of size BITS/8, and each group
                 is converted to a number as with pack()/unpack()
                 with big-endian formats `n'/`N' (and analoguously
                 for BITS==64).  See the section on "pack" for
                 details.
    
                 If bits is 4 or less, the string is broken into
                 bytes, then the bits of each byte are broken into
                 8/BITS groups.  Bits of a byte are numbered in a
                 little-endian-ish way, as in `0x01', `0x02', `0x04',
                 `0x08', `0x10', `0x20', `0x40', `0x80'.  For
                 example, breaking the single input byte `chr(0x36)'
                 into two groups gives a list `(0x6, 0x3)'; breaking
                 it into 4 groups gives `(0x2, 0x1, 0x3, 0x0)'.
    
                 `vec' may also be assigned to, in which case
                 parentheses are needed to give the expression the
                 correct precedence as in
    
                     vec($image, $max_x * $x + $y, 8) = 3;
    
                 If the selected element is off the end of the
                 string, the value 0 is returned.  If an element off
                 the end of the string is written to, Perl will first
                 extend the string with sufficiently many zero bytes.
    
                 Strings created with `vec' can also be manipulated
                 with the logical operators `|', `&', `^', and `~'.
                 These operators will assume a bit vector operation
                 is desired when both operands are strings.  See the
                 Bitwise String Operators entry in the perlop
                 manpage.
    
                 The following code will build up an ASCII string
                 saying `'PerlPerlPerl''.  The comments show the
                 string after each step.  Note that this code works
                 in the same way on big-endian or little-endian
                 machines.
    
                     my $foo = '';
                     vec($foo,  0, 32) = 0x5065726C;     # 'Perl'
    
                     # $foo eq "Perl" eq "\x50\x65\x72\x6C", 32 bits
                     print vec($foo, 0, 8);              # prints 80 == 0x50 == ord('P')
    
                     vec($foo,  2, 16) = 0x5065;         # 'PerlPe'
                     vec($foo,  3, 16) = 0x726C;         # 'PerlPerl'
                     vec($foo,  8,  8) = 0x50;           # 'PerlPerlP'
                     vec($foo,  9,  8) = 0x65;           # 'PerlPerlPe'
                     vec($foo, 20,  4) = 2;              # 'PerlPerlPe'   . "\x02"
                     vec($foo, 21,  4) = 7;              # 'PerlPerlPer'
                                                         # 'r' is "\x72"
                     vec($foo, 45,  2) = 3;              # 'PerlPerlPer'  . "\x0c"
                     vec($foo, 93,  1) = 1;              # 'PerlPerlPer'  . "\x2c"
                     vec($foo, 94,  1) = 1;              # 'PerlPerlPerl'
                                                         # 'l' is "\x6c"
    
                 To transform a bit vector into a string or list of
                 0's and 1's, use these:
    
                     $bits = unpack("b*", $vector);
                     @bits = split(//, unpack("b*", $vector));
    
                 If you know the exact length in bits, it can be used
                 in place of the `*'.
    
                 Here is an example to illustrate how the bits
                 actually fall in place:
    
                     #!/usr/bin/perl -wl
    
                     print <<'EOT';
                                                       0         1         2         3
                                        unpack("V",$_) 01234567890123456789012345678901
                     ------------------------------------------------------------------
                     EOT
    
                     for $w (0..3) {
                         $width = 2**$w;
                         for ($shift=0; $shift < $width; ++$shift) {
                             for ($off=0; $off < 32/$width; ++$off) {
                                 $str = pack("B*", "0"x32);
                                 $bits = (1<<$shift);
                                 vec($str, $off, $width) = $bits;
                                 $res = unpack("b*",$str);
                                 $val = unpack("V", $str);
                                 write;
                             }
                         }
                     }
    
                     format STDOUT =
                     vec($_,@#,@#) = @<< == @######### @>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
                     $off, $width, $bits, $val, $res
                     .
                     __END__
    
                 Regardless of the machine architecture on which it
                 is run, the above example should print the following
                 table:
    
    
    
                                                       0         1         2         3
                                        unpack("V",$_) 01234567890123456789012345678901
                     ------------------------------------------------------------------
                     vec($_, 0, 1) = 1   ==          1 10000000000000000000000000000000
                     vec($_, 1, 1) = 1   ==          2 01000000000000000000000000000000
                     vec($_, 2, 1) = 1   ==          4 00100000000000000000000000000000
                     vec($_, 3, 1) = 1   ==          8 00010000000000000000000000000000
                     vec($_, 4, 1) = 1   ==         16 00001000000000000000000000000000
                     vec($_, 5, 1) = 1   ==         32 00000100000000000000000000000000
                     vec($_, 6, 1) = 1   ==         64 00000010000000000000000000000000
                     vec($_, 7, 1) = 1   ==        128 00000001000000000000000000000000
                     vec($_, 8, 1) = 1   ==        256 00000000100000000000000000000000
                     vec($_, 9, 1) = 1   ==        512 00000000010000000000000000000000
                     vec($_,10, 1) = 1   ==       1024 00000000001000000000000000000000
                     vec($_,11, 1) = 1   ==       2048 00000000000100000000000000000000
                     vec($_,12, 1) = 1   ==       4096 00000000000010000000000000000000
                     vec($_,13, 1) = 1   ==       8192 00000000000001000000000000000000
                     vec($_,14, 1) = 1   ==      16384 00000000000000100000000000000000
                     vec($_,15, 1) = 1   ==      32768 00000000000000010000000000000000
                     vec($_,16, 1) = 1   ==      65536 00000000000000001000000000000000
                     vec($_,17, 1) = 1   ==     131072 00000000000000000100000000000000
                     vec($_,18, 1) = 1   ==     262144 00000000000000000010000000000000
                     vec($_,19, 1) = 1   ==     524288 00000000000000000001000000000000
                     vec($_,20, 1) = 1   ==    1048576 00000000000000000000100000000000
                     vec($_,21, 1) = 1   ==    2097152 00000000000000000000010000000000
                     vec($_,22, 1) = 1   ==    4194304 00000000000000000000001000000000
                     vec($_,23, 1) = 1   ==    8388608 00000000000000000000000100000000
                     vec($_,24, 1) = 1   ==   16777216 00000000000000000000000010000000
                     vec($_,25, 1) = 1   ==   33554432 00000000000000000000000001000000
                     vec($_,26, 1) = 1   ==   67108864 00000000000000000000000000100000
                     vec($_,27, 1) = 1   ==  134217728 00000000000000000000000000010000
                     vec($_,28, 1) = 1   ==  268435456 00000000000000000000000000001000
                     vec($_,29, 1) = 1   ==  536870912 00000000000000000000000000000100
                     vec($_,30, 1) = 1   == 1073741824 00000000000000000000000000000010
                     vec($_,31, 1) = 1   == 2147483648 00000000000000000000000000000001
                     vec($_, 0, 2) = 1   ==          1 10000000000000000000000000000000
                     vec($_, 1, 2) = 1   ==          4 00100000000000000000000000000000
                     vec($_, 2, 2) = 1   ==         16 00001000000000000000000000000000
                     vec($_, 3, 2) = 1   ==         64 00000010000000000000000000000000
                     vec($_, 4, 2) = 1   ==        256 00000000100000000000000000000000
                     vec($_, 5, 2) = 1   ==       1024 00000000001000000000000000000000
                     vec($_, 6, 2) = 1   ==       4096 00000000000010000000000000000000
                     vec($_, 7, 2) = 1   ==      16384 00000000000000100000000000000000
                     vec($_, 8, 2) = 1   ==      65536 00000000000000001000000000000000
                     vec($_, 9, 2) = 1   ==     262144 00000000000000000010000000000000
                     vec($_,10, 2) = 1   ==    1048576 00000000000000000000100000000000
                     vec($_,11, 2) = 1   ==    4194304 00000000000000000000001000000000
                     vec($_,12, 2) = 1   ==   16777216 00000000000000000000000010000000
                     vec($_,13, 2) = 1   ==   67108864 00000000000000000000000000100000
                     vec($_,14, 2) = 1   ==  268435456 00000000000000000000000000001000
                     vec($_,15, 2) = 1   == 1073741824 00000000000000000000000000000010
                     vec($_, 0, 2) = 2   ==          2 01000000000000000000000000000000
                     vec($_, 1, 2) = 2   ==          8 00010000000000000000000000000000
                     vec($_, 2, 2) = 2   ==         32 00000100000000000000000000000000
                     vec($_, 3, 2) = 2   ==        128 00000001000000000000000000000000
                     vec($_, 4, 2) = 2   ==        512 00000000010000000000000000000000
                     vec($_, 5, 2) = 2   ==       2048 00000000000100000000000000000000
                     vec($_, 6, 2) = 2   ==       8192 00000000000001000000000000000000
                     vec($_, 7, 2) = 2   ==      32768 00000000000000010000000000000000
                     vec($_, 8, 2) = 2   ==     131072 00000000000000000100000000000000
                     vec($_, 9, 2) = 2   ==     524288 00000000000000000001000000000000
                     vec($_,10, 2) = 2   ==    2097152 00000000000000000000010000000000
                     vec($_,11, 2) = 2   ==    8388608 00000000000000000000000100000000
                     vec($_,12, 2) = 2   ==   33554432 00000000000000000000000001000000
                     vec($_,13, 2) = 2   ==  134217728 00000000000000000000000000010000
                     vec($_,14, 2) = 2   ==  536870912 00000000000000000000000000000100
                     vec($_,15, 2) = 2   == 2147483648 00000000000000000000000000000001
                     vec($_, 0, 4) = 1   ==          1 10000000000000000000000000000000
                     vec($_, 1, 4) = 1   ==         16 00001000000000000000000000000000
                     vec($_, 2, 4) = 1   ==        256 00000000100000000000000000000000
                     vec($_, 3, 4) = 1   ==       4096 00000000000010000000000000000000
                     vec($_, 4, 4) = 1   ==      65536 00000000000000001000000000000000
                     vec($_, 5, 4) = 1   ==    1048576 00000000000000000000100000000000
                     vec($_, 6, 4) = 1   ==   16777216 00000000000000000000000010000000
                     vec($_, 7, 4) = 1   ==  268435456 00000000000000000000000000001000
                     vec($_, 0, 4) = 2   ==          2 01000000000000000000000000000000
                     vec($_, 1, 4) = 2   ==         32 00000100000000000000000000000000
                     vec($_, 2, 4) = 2   ==        512 00000000010000000000000000000000
                     vec($_, 3, 4) = 2   ==       8192 00000000000001000000000000000000
                     vec($_, 4, 4) = 2   ==     131072 00000000000000000100000000000000
                     vec($_, 5, 4) = 2   ==    2097152 00000000000000000000010000000000
                     vec($_, 6, 4) = 2   ==   33554432 00000000000000000000000001000000
                     vec($_, 7, 4) = 2   ==  536870912 00000000000000000000000000000100
                     vec($_, 0, 4) = 4   ==          4 00100000000000000000000000000000
                     vec($_, 1, 4) = 4   ==         64 00000010000000000000000000000000
                     vec($_, 2, 4) = 4   ==       1024 00000000001000000000000000000000
                     vec($_, 3, 4) = 4   ==      16384 00000000000000100000000000000000
                     vec($_, 4, 4) = 4   ==     262144 00000000000000000010000000000000
                     vec($_, 5, 4) = 4   ==    4194304 00000000000000000000001000000000
                     vec($_, 6, 4) = 4   ==   67108864 00000000000000000000000000100000
                     vec($_, 7, 4) = 4   == 1073741824 00000000000000000000000000000010
                     vec($_, 0, 4) = 8   ==          8 00010000000000000000000000000000
                     vec($_, 1, 4) = 8   ==        128 00000001000000000000000000000000
                     vec($_, 2, 4) = 8   ==       2048 00000000000100000000000000000000
                     vec($_, 3, 4) = 8   ==      32768 00000000000000010000000000000000
                     vec($_, 4, 4) = 8   ==     524288 00000000000000000001000000000000
                     vec($_, 5, 4) = 8   ==    8388608 00000000000000000000000100000000
                     vec($_, 6, 4) = 8   ==  134217728 00000000000000000000000000010000
                     vec($_, 7, 4) = 8   == 2147483648 00000000000000000000000000000001
                     vec($_, 0, 8) = 1   ==          1 10000000000000000000000000000000
                     vec($_, 1, 8) = 1   ==        256 00000000100000000000000000000000
                     vec($_, 2, 8) = 1   ==      65536 00000000000000001000000000000000
                     vec($_, 3, 8) = 1   ==   16777216 00000000000000000000000010000000
                     vec($_, 0, 8) = 2   ==          2 01000000000000000000000000000000
                     vec($_, 1, 8) = 2   ==        512 00000000010000000000000000000000
                     vec($_, 2, 8) = 2   ==     131072 00000000000000000100000000000000
                     vec($_, 3, 8) = 2   ==   33554432 00000000000000000000000001000000
                     vec($_, 0, 8) = 4   ==          4 00100000000000000000000000000000
                     vec($_, 1, 8) = 4   ==       1024 00000000001000000000000000000000
                     vec($_, 2, 8) = 4   ==     262144 00000000000000000010000000000000
                     vec($_, 3, 8) = 4   ==   67108864 00000000000000000000000000100000
                     vec($_, 0, 8) = 8   ==          8 00010000000000000000000000000000
                     vec($_, 1, 8) = 8   ==       2048 00000000000100000000000000000000
                     vec($_, 2, 8) = 8   ==     524288 00000000000000000001000000000000
                     vec($_, 3, 8) = 8   ==  134217728 00000000000000000000000000010000
                     vec($_, 0, 8) = 16  ==         16 00001000000000000000000000000000
                     vec($_, 1, 8) = 16  ==       4096 00000000000010000000000000000000
                     vec($_, 2, 8) = 16  ==    1048576 00000000000000000000100000000000
                     vec($_, 3, 8) = 16  ==  268435456 00000000000000000000000000001000
                     vec($_, 0, 8) = 32  ==         32 00000100000000000000000000000000
                     vec($_, 1, 8) = 32  ==       8192 00000000000001000000000000000000
                     vec($_, 2, 8) = 32  ==    2097152 00000000000000000000010000000000
                     vec($_, 3, 8) = 32  ==  536870912 00000000000000000000000000000100
                     vec($_, 0, 8) = 64  ==         64 00000010000000000000000000000000
                     vec($_, 1, 8) = 64  ==      16384 00000000000000100000000000000000
                     vec($_, 2, 8) = 64  ==    4194304 00000000000000000000001000000000
                     vec($_, 3, 8) = 64  == 1073741824 00000000000000000000000000000010
                     vec($_, 0, 8) = 128 ==        128 00000001000000000000000000000000
                     vec($_, 1, 8) = 128 ==      32768 00000000000000010000000000000000
                     vec($_, 2, 8) = 128 ==    8388608 00000000000000000000000100000000
                     vec($_, 3, 8) = 128 == 2147483648 00000000000000000000000000000001
    
    
         wait    Behaves like the wait(2) system call on your system:
                 it waits for a child process to terminate and
                 returns the pid of the deceased process, or `-1' if
                 there are no child processes.  The status is
                 returned in `$?'.  Note that a return value of `-1'
                 could mean that child processes are being
                 automatically reaped, as described in the perlipc
                 manpage.
    
         waitpid PID,FLAGS
                 Waits for a particular child process to terminate
                 and returns the pid of the deceased process, or `-1'
                 if there is no such child process.  On some systems,
                 a value of 0 indicates that there are processes
                 still running.  The status is returned in `$?'.  If
                 you say
    
                     use POSIX ":sys_wait_h";
                     #...
                     do {
                         $kid = waitpid(-1,&WNOHANG);
                     } until $kid == -1;
    
                 then you can do a non-blocking wait for all pending
                 zombie processes.  Non-blocking wait is available on
                 machines supporting either the waitpid(2) or
                 wait4(2) system calls.  However, waiting for a
                 particular pid with FLAGS of `0' is implemented
                 everywhere.  (Perl emulates the system call by
                 remembering the status values of processes that have
                 exited but have not been harvested by the Perl
                 script yet.)
    
                 Note that on some systems, a return value of `-1'
                 could mean that child processes are being
                 automatically reaped.  See the perlipc manpage for
                 details, and for other examples.
    
         wantarray
                 Returns true if the context of the currently
                 executing subroutine is looking for a list value.
                 Returns false if the context is looking for a
                 scalar.  Returns the undefined value if the context
                 is looking for no value (void context).
    
                     return unless defined wantarray;    # don't bother doing more
                     my @a = complex_calculation();
                     return wantarray ? @a : "@a";
    
                 This function should have been named wantlist()
                 instead.
    
         warn LIST
                 Produces a message on STDERR just like `die', but
                 doesn't exit or throw an exception.
    
                 If LIST is empty and `$@' already contains a value
                 (typically from a previous eval) that value is used
                 after appending `"\t...caught"' to `$@'.  This is
                 useful for staying almost, but not entirely similar
                 to `die'.
    
                 If `$@' is empty then the string `"Warning:
                 Something's wrong"' is used.
    
                 No message is printed if there is a `$SIG{__WARN__}'
                 handler installed.  It is the handler's
                 responsibility to deal with the message as it sees
                 fit (like, for instance, converting it into a
                 `die').  Most handlers must therefore make
                 arrangements to actually display the warnings that
                 they are not prepared to deal with, by calling
                 `warn' again in the handler.  Note that this is
                 quite safe and will not produce an endless loop,
                 since `__WARN__' hooks are not called from inside
                 one.
    
                 You will find this behavior is slightly different
                 from that of `$SIG{__DIE__}' handlers (which don't
                 suppress the error text, but can instead call `die'
                 again to change it).
    
                 Using a `__WARN__' handler provides a powerful way
                 to silence all warnings (even the so-called
                 mandatory ones).  An example:
    
                     # wipe out *all* compile-time warnings
                     BEGIN { $SIG{'__WARN__'} = sub { warn $_[0] if $DOWARN } }
                     my $foo = 10;
                     my $foo = 20;          # no warning about duplicate my $foo,
                                            # but hey, you asked for it!
                     # no compile-time or run-time warnings before here
                     $DOWARN = 1;
    
                     # run-time warnings enabled after here
                     warn "\$foo is alive and $foo!";     # does show up
    
                 See the perlvar manpage for details on setting
                 `%SIG' entries, and for more examples.  See the Carp
                 module for other kinds of warnings using its carp()
                 and cluck() functions.
    
         write FILEHANDLE
    
         write EXPR
    
         write   Writes a formatted record (possibly multi-line) to
                 the specified FILEHANDLE, using the format
                 associated with that file.  By default the format
                 for a file is the one having the same name as the
                 filehandle, but the format for the current output
                 channel (see the `select' function) may be set
                 explicitly by assigning the name of the format to
                 the `$~' variable.
    
                 Top of form processing is handled automatically:  if
                 there is insufficient room on the current page for
                 the formatted record, the page is advanced by
                 writing a form feed, a special top-of-page format is
                 used to format the new page header, and then the
                 record is written.  By default the top-of-page
                 format is the name of the filehandle with "_TOP"
                 appended, but it may be dynamically set to the
                 format of your choice by assigning the name to the
                 `$^' variable while the filehandle is selected.  The
                 number of lines remaining on the current page is in
                 variable `$-', which can be set to `0' to force a
                 new page.
    
                 If FILEHANDLE is unspecified, output goes to the
                 current default output channel, which starts out as
                 STDOUT but may be changed by the `select' operator.
                 If the FILEHANDLE is an EXPR, then the expression is
                 evaluated and the resulting string is used to look
                 up the name of the FILEHANDLE at run time.  For more
                 on formats, see the perlform manpage.
    
                 Note that write is not the opposite of `read'.
                 Unfortunately.
    
         y///    The transliteration operator.  Same as `tr///'.  See
                 the perlop manpage.
    
    
    
    


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