There is so much ambiguity in language that parallelization is often possible at a very course-grained level. This usually doesn't require more cleverness than

There is so much ambiguity in language that parallelization is often possible at a very course-grained level. This usually doesn't require more cleverness than multi-processing or multi-threading. Given that they switched from their own pattern matching language to an optimized WAM, I suspect they use one of the common Prolog implementations.