[Haskell] Evil code

[Thomas Davie]

Hello list,
   I am in the process of testing a debugger, and need some examples  
to throw at it.  It's based on hat, so the normal rules about nothing  
that uses glasgow extensions or ffi apply.  But I'm hitting a bit of  
a wall.  Do any of you have some examples of nasty uses of higher  
order code.  For example CPS, or non-IO monads.

TIA

Bob