Does the student understand the code? A simple way to find out: place the student a room and ask them to rewrite the code. Allow them access to perldoc if requested. If they can rewrite the program to work as it should, I don't see much of a problem (skip to the next paragraph). If they can't I can think of lots of fun assignments to give them (including a very complete, line by line analysis of the plagiarized code).

Also, a couple thousand word essay on the history of copyright law in your country including what its intended purpose is would be in order. There's no reason why this can't be converted into a positive experience.