All this talk of IO and exceptions reminds me of a small issue I've been having. I like Control.Monad.Error but often my stuff is threaded through the IO monad so, AFAICT from the functional dependency stuff, that means my errors have to be IOErrors. Is that right? And, then, I want control over what's actually reported to the user, but if I make a userError than the consequent message (where the details are presumably platform-dependent) is wrapped up in extra text that I didn't want appearing. Can I use Control.Monad.Error for IO monad stuff such that I can control what string will appear when my error handler tries to "show" my exception? Admittedly, I'm still learning my way around this bit of the standard libraries, so I may have missed something obvious. -- Mark