[Haskell-cafe] global, modifiable variable for debugging

Hi, I have a program with a debug flag in it (Strangely I've yet to be able to write bug-free code). I'd like to change the state of the debug flag based on command line args. I looked at IOVar but that would cause all the pure procedures to get swallowed by the IO Monad. Is a better way to get this behavior ? Thanks, Brian