#!/usr/bin/perl -w

use strict;

my @one = qw{C A T};
my @two = qw{D O G};
my @three = qw{B I R D};

my @combos = permute(\@one, \@two, \@three);
show_text(\@combos, \@one, \@two, \@three);

sub permute {
	my @arrays = @_;
	my @lengths;
	foreach my $array_ref (@arrays) {
		push @lengths, scalar @$array_ref;
	}
	return combine(@lengths);
}

sub combine {
	my $length = shift;
	my @results;
	for (0 .. ($length - 1)) {
		if (@_) {
			foreach my $result (combine(@_)) {
				push @results, $_ . $result;
			}
		} else {
			push @results, $_;
		}
	}
	return @results;
}

sub show_text {
	my ($combos, @arrays) = @_;
	foreach my $combo (@$combos) {
		my $i = 0;
		my $text = '';
		foreach my $elem (split'', $combo) {
			$text .= $arrays[$i++]->[$elem];
		}
		print "$text\n";
	}
}