AI::Prolog seems to offer all the advantages of the procedural programming language from Prolog and the flexibility of Perl. Constructing the various rules to cover all events which will be used to determine that a “deal has been done” will be difficult.
In conversations the same sentences are not normally used again and again nor words in the same order, this will play havoc with predicates (rules and structures, new rules will need to be constantly added to cover changing speech patterns and vocabulary, therefore getting anything like 100% accuracy is not likely.
But maybe that sort of accuracy is not required.
Perhaps you could post a sample conversation so we can get an idea of what is involved.
A couple of quick notes. First, AI::Prolog is useful when there's simple pattern matching, but it's very slow. If you have a large search space, it's unusable. Also, I've always wanted to add support for DCDs (declarative clause grammars) which would make natural language processing much easier.