More rules

ruleStatement = do
    exp <- ruleExpression
    f <- option return $ choice
        [ rulePostConditional
        , rulePostLoop
        , rulePostIterate
        ]
    f exp

say "YAPC was great" if $cakes.yummy

• choice means try out a few parsers
• the first that matches wins, otherwise backtrack
• if none succeeded, the choice fails
• in this case, it's protected by an option, letting you provide a fallback