gcd.pl

#!/usr/bin/env perl

# Usage:
# $ perl gcd.pl 11 22 33 121
# 11

use strict;
use warnings;
use utf8;
use integer;
use List::Util qw/ reduce /;

sub gcd2 {
  my ( $a, $b ) = @_;
  $b == 0 ? $a : gcd2( $b, $a % $b );
}

# http://stackoverflow.com/questions/1490505/how-do-i-prevent-listmoreutils-from-warning-about-using-a-and-b-only-once
sub gcdn {
  our ( $a, $b );
  reduce { gcd2( $a, $b ) } 0, @_;
}

print gcdn(@ARGV), "\n";