Isn't the lack of a stateful REPL a feature in Haskell? Don't get my wrong, I love image/state-based developing (having working knowledge with SmallTalk and just getting into emacs). But I think it is quite haskelly to introduce functions that create the state rather than create the state interactively yourself. This should be good for mocking and tests also. Yes, this is more work than in most other practical languages, but this is Haskell for you ;)