#!/usr/bin/perl -w
use strict;

my @array = (
    [ 'a', 'b', 'c' ],
    [ 1, 2 ],
    ['x', 'y', 'z'],
    [7, 8, 9]
);

sub permute {                 # merlyn's
  my $last = pop @_;
  unless (@_) {
    return map [$_], @$last;
  }
  return map { my $left = $_; map [@$left, $_], @$last } permute(@_);
}

print  join("", @$_), " " for permute(@array);
print "\n";
__END__
a1x7 a1x8 a1x9         a1y7 a1y8 a1y9         a1z7 a1z8 a1z9
a2x7 a2x8 a2x9         a2y7 a2y8 a2y9         a2z7 a2z8 a2z9
b1x7 b1x8 b1x9         b1y7 b1y8 b1y9         b1z7 b1z8 b1z9
b2x7 b2x8 b2x9         b2y7 b2y8 b2y9         b2z7 b2z8 b2z9
c1x7 c1x8 c1x9         c1y7 c1y8 c1y9         c1z7 c1z8 c1z9
c2x7 c2x8 c2x9         c2y7 c2y8 c2y9         c2z7 c2z8 c2z9