[Haskell-beginners] Problem with GHCI.

Could anyone tell me why this might be happening? I was trying to add some modules to the GHCi(:d +...). Couldn't match expected type `String -> IO String' against inferred type `()' In the expression: () In the expression: () :: String -> IO String In the definition of `__cmCompileExpr': __cmCompileExpr = () :: String -> IO String Thank you.