[Haskell-beginners] Parse error

Hi, I am trying to run the following from the GHCi command prompt which results in parse error. -------------- Prelude> :{ Prelude| foo :: Maybe String Prelude| foo = do Prelude| x <- Just 3 Prelude| y <- Just "!" Prelude| Just (show x ++ y) Prelude| :} <interactive>:145:5: parse error on input `=' --------------- Any help would be appreciated. Thanks, Shishir