#!/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;
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