How do you do an in-place quicksort in Haskell

Could somebody provide an in-place quicksort haskell function? I.e. it returns a new sorted list, but the input list is copied to a mutable array or something.

I want to see how to do this, because I have a performance critical program where i need to simulate races and tally scores. If I use immutable data structures for this, each race will take O(log(numRaces) + numRunners) time, whereas if I use mutable arrays etc, each race will take O(log(numRaces)) time.

oh by the way i didn't actually need to do quicksort, i just wanted an example to see how to use mutable arrays effectively