OK, I'm new to this, but thought I would have a go. On my own I get: $d="ABCDEFGFEDCBA"; for($i=71;$i>64;$i-=1) { print "$d\n"; $c=chr($i); $d =~ s/$c/ /g; } With a little help, I then got: $_="ABCDEFGFEDCBA\n";for $r(reverse(A..G)){print; s/$r/ /g} Same theory, better solution.