Reference example for using the Getopt::Std Perl module

getopt-std.pl

use strict;
use warnings;
use feature qw(say);
use Getopt::Std;

# If set to true, exit script after processing --help or --version flags
$Getopt::Std::STANDARD_HELP_VERSION = 1;
our $VERSION = "0.1";

#------------------------------------------------------------------------------#
# Options
#------------------------------------------------------------------------------#

my %opts;

# -f requires an argument, -l does not take an argument
getopts('f:l', \%opts) or abort();

say "Supplied options:";

if (defined $opts{f}) {
  say "-f $opts{f}";
}

if (defined $opts{l}) {
  say "-l $opts{l}";
}

#------------------------------------------------------------------------------#
# Positional Arguments
#------------------------------------------------------------------------------#

# Note: positional arguments must be specified AFTER all options on the command
# line. There may be a double-dash (--) between options and arguments.

say "Trailing positional arguments (" . scalar(@ARGV) . "):";

for my $i (0 .. $#ARGV) {
  say $ARGV[$i];
}

#------------------------------------------------------------------------------#
# Subroutines
#------------------------------------------------------------------------------#

# Called by Getopt::Std when supplying --help option
sub HELP_MESSAGE {
  say get_help_message();
}

# Called by Getopt::Std when supplying --version or --help option
sub VERSION_MESSAGE {
  say "Version $VERSION";
}

# Abort script due to error (e.g. invalid command line options)
sub abort {
  say get_help_message();
  exit 1;
}

# Central help message
sub get_help_message {
  return "Hi, I'm the help message :)";
}