greet.hs

-- This works as I'd expect.
module Main where
  main = do
    name <- getContents
    putStrLn $ "Hello, " ++ "Ben" ++ "!"

=> "Hello, Ben!"
> :type "Ben"   -- [Char]


-- In this case, the final string isn't concatenated. 
module Main where
  main = do
    name <- getContents
    putStrLn $ "Hello, " ++ name ++ "!"

=> "Hello, Ben"
> :type name   -- String