I notice that Prelude.catch and Exception.catch behave differently, even though they both have the same type signature (and name). Exception.catch catches exceptions that Prelude.catch does not.

Prelude.catch catches IO exceptions only, because this is what the Haskell report specifies. i.e. the meaning of Prelude.catch undefined (\e -> return 42) should be undefined rather than 'return 42'. We can't change the meaning of Prelude.catch without deviating from Haskell 98. The idea is that if you want to use Exceptions in their full glory, you: import Prelude hiding (catch) import Exception or (my favourite) import qualified Exception Cheers, Simon