[galaxy-dev] Newbie question, adding a custom perl script

Hi, A co-worker has a perl script that takes a directory path, and then interates over a the file in that directory and processes them into an output directory. I want to integrate that into galaxy. I've figured out that I'll need to create a tool XML conf with the inputs , outputs etc. My question is what param type should I use for a directory, in the input and output ? Or maybe what I'm looking for a is an input, output type that is a set of file (rather than tying it to a filesystem) Sorry for my beginners questions ! Thanks Mac