@sudorandom Probably Mercury from University of Melbourne

Sadly the bits taken from Prolog are a bit too front and centre (eg in the syntax) which scares people off.

But it has a good type system (including Haskell-like type classes) and handles state-mutation and real-world modification much more cleanly and simply than the monad-like approach of Haskell (or bodges in other languages).

The Prolog-like logic-language features are actually not super useful (beyond the usual places they shine, like constraint solving. It's kinda sad in a way they've come to dominate how people see the language.