If "originality" is your goal, lots of experiments with GP have already been done. There should be some room for more, however. Some resources to examine first (that don't necessarily stay within the bounds of Perl) are:

• the garage
• geneticprogramming.com
• look under 'evolutionary computation'; if you can get hold of one of his papers, they're quite interesting
• CS bibliography; a useful resource; you'll probably also have to go to a library to do further research

As an interesting and strange coincidence, I just started reading a book titled The Monk in the Garden by Robin Marantz Henig. If you didn't guess from the title, it's about Gregor Mendel.