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Getopt::Std(3pm)       Perl Programmers Reference Guide       Getopt::Std(3pm)
NAME
       Getopt::Std - Process single-character switches with switch clustering
SYNOPSIS
           use Getopt::Std;
           getopts('oif:');  # -o & -i are boolean flags, -f takes an argument
                             # Sets $opt_* as a side effect.
           getopts('oif:', \%opts);  # options as above. Values in %opts
           getopt('oDI');    # -o, -D & -I take arg.
                             # Sets $opt_* as a side effect.
           getopt('oDI', \%opts);    # -o, -D & -I take arg.  Values in %opts
DESCRIPTION
       The "getopts()" function processes single-character switches with
       switch clustering.  Pass one argument which is a string containing all
       switches to be recognized.  For each switch found, if an argument is
       expected and provided, "getopts()" sets $opt_x (where "x" is the switch
       name) to the value of the argument.  If an argument is expected but
       none is provided, $opt_x is set to an undefined value.  If a switch
       does not take an argument, $opt_x is set to 1.
       Switches which take an argument don't care whether there is a space
       between the switch and the argument.  If unspecified switches are found
       on the command-line, the user will be warned that an unknown option was
       given.
       The "getopts()" function returns true unless an invalid option was
       found.
       The "getopt()" function is similar, but its argument is a string
       containing all switches that take an argument.  If no argument is
       provided for a switch, say, "y", the corresponding $opt_y will be set
       to an undefined value.  Unspecified switches are silently accepted.
       Use of "getopt()" is not recommended.
       Note that, if your code is running under the recommended "use strict
       vars" pragma, you will need to declare these package variables with
       "our":
           our($opt_x, $opt_y);
       For those of you who don't like additional global variables being
       created, "getopt()" and "getopts()" will also accept a hash reference
       as an optional second argument.  Hash keys will be "x" (where "x" is
       the switch name) with key values the value of the argument or 1 if no
       argument is specified.
       To allow programs to process arguments that look like switches, but
       aren't, both functions will stop processing switches when they see the
       argument "--".  The "--" will be removed from @ARGV.
"--help" and "--version"
       If "-" is not a recognized switch letter, getopts() supports arguments
       "--help" and "--version".  If "main::HELP_MESSAGE()" and/or
       "main::VERSION_MESSAGE()" are defined, they are called; the arguments
       are the output file handle, the name of option-processing package, its
       version, and the switches string.  If the subroutines are not defined,
       an attempt is made to generate intelligent messages; for best results,
       define $main::VERSION.
       If embedded documentation (in pod format, see perlpod) is detected in
       the script, "--help" will also show how to access the documentation.
       Note that due to excessive paranoia, if
       $Getopt::Std::STANDARD_HELP_VERSION isn't true (the default is false),
       then the messages are printed on STDERR, and the processing continues
       after the messages are printed.  This being the opposite of the
       standard-conforming behaviour, it is strongly recommended to set
       $Getopt::Std::STANDARD_HELP_VERSION to true.
       One can change the output file handle of the messages by setting
       $Getopt::Std::OUTPUT_HELP_VERSION.  One can print the messages of
       "--help" (without the "Usage:" line) and "--version" by calling
       functions help_mess() and version_mess() with the switches string as an
       argument.
perl v5.26.3                      2018-03-23                  Getopt::Std(3pm)