For example, I have big load of urls to crawl. Urls can be split to multiple chunks. Basex can start multiple function calls in parallel that deals one chunk. After functions finished, we can merge results. This is basic way.
Haskell provides the Strategies library for that:
http://hackage.haskell.org/package/parallel-3.1.0.1/docs/Control-Parallel-St...
It would be rather easy to implement some first quick hacks that provide simple multi-threading, but it gets a real challenge if you want to make the feature production safe. This is different for languages like Clojure, because parallel programming is at the very core of the language.