Maybe I, The Cause Of The Thousand Rants, can have a word in this. ;-)
I've benchmarked File::Find and the recursive opendir stunt and my conclusions are theese:
Use File::Find on Unix, It's much faster than other methods there. In the sub, put /\.mp3$/ before -f (because that's faster!).
On Win32 the recursive opendir method is faster, or at least as fast if you want to match /\.mp3$/.
BUT DON'T FORGET TO CHECK FOR SYMBOLIC LINKS ON *NIX if you choose to do recursive opendir there...

/brother t0mas