how do I abstract this pattern ?

Suppose p1, p2, p3 are 3 predicates that take an input -- say, a String. They return either (True, result) or False. I want to get an effect like in this expression: case p1 s of (True, r) -> r False -> case p2 s of (True, r) -> r False -> case p3 s of (True, r) -> r False -> none Is this a job for Maybe monad ? How do I do that ? Thanks HP