Well, sort of. Ok, we can parse that. Let's assume a variable x holds the output of :show modules as a String. We call lines on it, then map words on it, do a !! 2 on it, and we get ["Util.hs,", "Recorder.hs,", "Game.hs,", "Monadius.hs,", "Demo.hs,"]. Chuck in a map (filter (\= ',')), and we get a good list. We can turn the list into a string suitable for hlint with a quick unwords.
So our long sought after command becomes ':def hoogle (\_ -> return $ ":! " ++ (unwords $ map (filter (\= ',')) $ (map words $ lines x) !! 2))'. But wait, how do we get 'x'? How do we call :show modules inside a Haskell expression? I have carefully looked over http://haskell.org/haskellwiki/GHC/GHCi#Using_GHCi and http://www.haskell.org/ghc/docs/latest/html/users_guide/ghci-commands.html and my conclusion is that you can't. You can't do a let x = :show modules, there is no function which will take ":show modules", and so on. :functions can accept Haskell output, but it's a one-way barrier. It's no good writing Haskell functions which need information from the :functions.
The first url includes a link to a .ghci mini-tutorial (section 4) that, among other things, implements :redir <var> <cmd> -- execute <cmd>, redirecting stdout to <var> Happy Holidays!-) Claus