I found this method from John Krahn who posts on some other Perl lists. It takes letters in any order and does the permutations.

Chris

#!/usr/bin/perl
use strict;
use warnings;

my @letters = qw /W A C K Y/;
my $pairings = 2;

for (0..@letters**$pairings-1) {
    my @combs;
    do {unshift @combs, $_ % @letters} while $_ = int $_ / @letters;
    unshift @combs, (0) x ($pairings - @combs);
    print "@letters[@combs]\n";
}
[download]