[Haskell-cafe] Help a Newbie

I am trying (and have been for quite some time) to repair a broken Haskell script.  I keep getting stuck on “Last generator in do {...} must be an expression”.  I am betting that this is not uncommon.  Can someone please help me understand? code5 :: Parser code5 = do dd <- code3 do ddd <- code3 do dddd <- code3 return "ce" code4 :: Parser code4 = do                         dd <- code3                         do dde <- code3                                     digit                                     ddd <- many (do digit)                                     q <- code5                                     return (q : "ss") Thanks in advance for helping Matthew