|laziness, impatience, and hubris|
Just as in every single large project, there are several levels to working on an AI program. I personally think Perl is eminently suited to certain aspects of AI development.
I, for one, am working on a program to play Go. I'm using pure Perl. Why? Because it's the easiest language I know to do effective proof-of-concepts in. It gives the highest-level datastructures I've ever seen, a ton of good modules that make the hard stuff easy and the impossible stuff merely hard, and pretty decent speed to boot! (So, Perl's a RAM hog. RAM's cheaper than my time!)
I'm working on the design for an intelligent MMRPG world. I will definitely be using Perl for the prototyping of the AI subroutines. I have some very different ideas on how to get (at least the simulation of) intelligent behavior. They don't fit very easily into my understanding of rules-based languages. Therefore, I will use the language I know best to do the initial stages.
Now, does this mean you have to release in Perl? Of course not! Go to the language(s) you feel are appropriate for the needs of the release. Do you need to squeeze RAM? CPU cycles? Different syntax needs? Maybe the team chooses another language? Are you getting subsidies from someone? There's all sorts of reasons to pick one language over another, and there's usually not enough discussion on which to choose.
Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.