This is an old thread, but agent based modeling (ABM) is still current as ever.

Perl-related links include this one by Guinevere Nell which has a nice example with perl code included.

For more extensive models at this moment two Java based platforms seem to rule: Ascape and Repast.

The complexity of both Ascape and Repast is high if you want to create your own models, but they both offer a nice interface to dabble with the standard models found in literature.

And making a basic model in Perl, as in the example of Guinevere Nell is relatively simple and fun. It will further your understanding under the hood of the model more than using the prefab ones.