gistfile1.pl

my $gs = Getopt::String->new({
  # --
  "" => sub { $_[0]->stop(); },
  # --help
  help => sub { print $usage; exit 1; },
  # --verbose[=n]
  verbose => sub {
    $verbosity = $_[0]->arg("Int", 1); # moose types. Second parameter is default
  },
  # --output filename
  output => sub {
    $outfile = $_[0]->arg("Str"); # undef fails Str validation
  },
  o => "output", # alias
});

my $remain = $gs->parse("...");