#!/usr/bin/env perl

use strict;
use warnings;

my %x = ( a => 1, b => 2 );
my %y = ( c => 3, d => 4 );
my %z = ( e => 5, f => 6 );

multi_for([\%x, \%y, \%z]);

sub multi_for {
    my ($hashes, $values, $index) = @_;
    $values = [] unless defined $values;
    $index = 0 unless defined $index;

    if ($#$hashes >= $index) {
        my %hash = %{$hashes->[$index]};
        for (sort keys %hash) {
            multi_for($hashes, [@$values, $hash{$_}], $index + 1);
        }
    }
    else {
        # Do something with $values, e.g.
        print "@$values\n";
    }
}

##</code><code>##

1 3 5
1 3 6
1 4 5
1 4 6
2 3 5
2 3 6
2 4 5
2 4 6