[popee]

At university we had to learn prolog and for me (C/perl) it was mind blowing experience. Fact that you are writing program as bunch of logical predicates was kind strange at first, but when you get used to it, it's such a great and powerful tool. Also, learning things like unification was just wooow. So, I'd recommend prolog to every programmer, especially today when most people use yet another standard language. On the other hand prolog is sooo out of the box.