Thanks. This looks like what I was looking for. I'll just make sure I understand it:

Pseudo-code:

use glob to expand filenames in /basedir
use grep to grab all directory names
for each directory name grab its subdirs
pass them onto map to where there matched to the regex
'.*/(.*?)$'
assign the (array) result from the map to the corresponding %dir key
[download]

I think I've got the basic idea of it, could someone explain how the subdir keys are assigned in the hash in a bit more detail? Thanks :)