need script

Certainly someone must have a script (preferably Perl)
laying around somewhere that will:

Recurse thru directories and rename files by replacing
any UPPER case characters with lower and replacing spaces
in the file names with something like underscores.

I suppose I could write one myself ( I struggle with
the recursion part), but if someone has one, and wouldn't mind
sharing, It would save me a ton of time and I would certainly be much appreciative.


Mike