For anyone who's interested, the next issue of The Perl Review will have an article entitled "Logic Programming in Perl." This will be a greatly expanded version of my OSCON talk on logic programming.
In this article, there will be a basic introduction to Prolog, via AI::Prolog. I will also be discussing its strengths and weaknesses vis a vis Perl and relational databases.
For those interested in the topic, it's also worth looking at Logic, a rather interesting take on logic programming by Luke Palmer. For much better performance, there's also Language::Prolog::Yaswi by Salvador Fandiño García. The latter allows you to access SWI-Prolog from Perl.