#!/usr/bin/perl 

use strict;
use warnings;
use Carp;

my @lines = ('A', 'B', 'C');
my @tojoin = qw/X Y W/;
my @new;

sub closure;

sub closure {
	my ($ary, $ret) = @_;
	
	if (length($ary->[0]) == 3)
	{
		return;
	}

	my @tmp;
	foreach (@$ary)
	{
		foreach my $to (@tojoin)
		{
			push @tmp, $_ . $to;	
		}
	}

	push @$ret, @tmp;

	closure \@tmp, $ret;
}

closure \@lines, \@new;

$, = ",";
print @new;