for my $num_digits (2..3) {
   for my $line (0 .. 4**$num_digits - 1) {

      my $remain = $line;
      my @digits;
      for (1..$depth) {
         push @digits, $remain % 4;
         $remain = int($remain / 4);
      }

      print(join(', ', @digits), "\n");
   }
}