use warnings;
use strict;
use Getopt::Long;

my @actions;
GetOptions(
  first  => sub { push @actions, \&first },
  second => sub { push @actions, \&second },
) or die "Invalid options passed to $0\n";

sub first {
  print "Processing sub first\n";
}

sub second {
  print "Processing sub second\n";
}

$_->() for @actions;

__END__

$ perl 11140961c.pl --first --second --first --second --second --first
Processing sub first
Processing sub second
Processing sub first
Processing sub second
Processing sub second
Processing sub first
$ perl 11140961c.pl --first --second --year --first --second --second --first
Unknown option: year
Invalid options passed to 11140961c.pl

##</code><code>##

use warnings;
use strict;
use Getopt::Long;

my $do_first = 0;
sub first { $do_first = 1 }

my $do_second = 0;
sub second { $do_second = 1 }

GetOptions(first=>\&first, second=>\&second)
	or die "Invalid options passed to $0\n";

if ($do_first) { print "First!\n" }

if ($do_second) { print "Second!\n" }

__END__

$ perl 11140961.pl --first --second --first --second --second --first
First!
Second!
$ perl 11140961.pl --first --second --year --first --second --second --first
Unknown option: year
Invalid options passed to 11140961.pl

##</code><code>##

use warnings;
use strict;
use Getopt::Long;

my @actions;
sub first { push @actions, 'first' }
sub second { push @actions, 'second' }

GetOptions(first=>\&first, second=>\&second)
	or die "Invalid options passed to $0\n";

for my $act (@actions) {
	if ($act eq 'first')
		{ print "First!\n" }
	elsif ($act eq 'second')
		{ print "Second!\n" }
	else { die $act } # shouldn't happen
}

__END__

$ perl 11140961b.pl --first --second --first --second --second --first
First!
Second!
First!
Second!
Second!
First!
$ perl 11140961b.pl --first --second --year --first --second --second --first
Unknown option: year
Invalid options passed to 11140961b.pl