[Haskell-cafe] Substituting values

Sometimes I'll need something like: if value == Foo then Bar else value Or some syntactic variation thereof: case value of { Foo -> Bar; _ -> value } Is there a better/shorter way to do it? I'm surprised that it's more complicated to substitute a value on its own than e.g. in a list, using filter. Or perhaps I'm missing the right abstraction? Thanks, Alvaro