I'm not sure why you're being downvoted. I don't know Haskell, but I had a look for the parser you mentioned and it does appear at first glance to use a fairly imperative-looking style, with loops and pointers into mutable data:

https://github.com/ocramz/xeno/blob/master/src/Xeno/DOM.hs

I would be interested in an analysis of this code from anyone who actually does know Haskell in case I'm misreading it.