Basicaly, you can't go it that way. Using the following line

    $result{$c1}{$c2}{$c3}{$c4}{$c5} .= $desc;

you always create a 5 level hash, and that's not what you want.

Also, your output example is not consistent. Basically you have some cases where you attach a leaf to a '0' on the hash table and in some other cases you attach it to a full number. Or do you want to have the '0' just on cases where the element has childs?

Now, how to help you to solve your problem.... first, I would use pattern matching instead of packs. second, you can't know if an element has more child or not before processing the remaining index. So, the structure you are using with in some cases a '0' and in some other without the '0' is complicated.

I hope this helps you to think a little more on your problem.