If you've never done any Java, you should learn it. It is so ubiquitous now that a lot of the most interesting writing about programming is written using Java, and some of the most interesting tools are written in Java. You may well decide you dislike it, but being able to read and understand it will help you a lot when you go to look at the current programming literature. It may also improve your knowledge of OO modeling, since that subject gets a lot more coverage in Java books than in Perl ones.