That's a very in-depth question. My best answer to that is that all depends on what you want to be able to do in python, if the answer is everything then get the
Perl Cookbook and flip through it until you've found parts of the book you don't understand; whatever you find is what else you have to learn. If your goal is only to know certain parts of perl, then i'd suggest writing out what you would like to be able to do well and making a sort-of checklist.