markong's suggestion to use Tree-Simple (instead of h-o-h) looks like a very good idea to me because it will easily allow you to traverse your file-system backwards - from the children back to the parent - (and forwards of course). Plus you can do all sorts of sorting and searching on filenames. Lastly, keys %hash returns keys in random order. So each run will not be consistent unless you always do sort keys %hash or use arrays. So, yes hash-of-hashes is a basic idea, but Tree-Simple will make it easier for you and it is a good thing to have in one's toolbelt.