If you want simple, you can always use Acme::Clean or if you have a sense of humor you can use Acme::Buffy.

I am working on my own commercial program written in perl and I was intending to modify Acme::Clean so that it displayed no code, just the license which the code is released under. While it does not keep someone from reversing what I had done, they cannot say, "I did not know that I was not supposed to do it".