I don't think such a thing exists. Not so sure but, the only "maintained" Perl based forums are YaBB & e-Blah. But these two are old-skool non-api things and you need to edit the code directly to add something AFAICT. However, I suggest trying MovableType Pro. It has a "Forum" feature (it really is a blog with different template set). Also, there is
but it's a kind of a toy with no roadmap I believe.