Flatten a directory with a filter in Clojure

I always wanted cross platform and stand-alone script to flatten a directory with an optional filter. I have relied on Ant builder from Groovy but it is slow and one needs to have Groovy installed along with Ant. So, I wrote a small script in Clojure that I can use and share with friends easily. Without further ado, here is the entire script:

Here is the source file for you to use, experiment or do whatever you want to have fun with Clojure.