I try to learn Haskell and struggle with converting do-syntax into monads.
So, I boiled it down to a tiny example.

I got this:

work :: String
work = do
    let arr = ["Get", "this", "to", "work"]
    let s = unlines arr
    s

main :: IO ()
main = putStrLn work

And I rephrase it to:

work :: String
work = ["Get", "this", "to", "work"] >>= unlines >>= return

main :: IO ()
main = putStrLn work

Which gave me:

monad-do.hs:2:42: error:  
    • Couldn't match type ‘Char’ with ‘[Char]’  
      Expected type: [Char] -> [Char]  
        Actual type: [String] -> String  
    • In the second argument of ‘(>>=)’, namely ‘unlines’  
      In the first argument of ‘(>>=)’, namely  
        ‘["Get", "this", "to", "work"] >>= unlines’  
      In the expression:  
        ["Get", "this", "to", "work"] >>= unlines >>= return  
  |  
2 | work = ["Get", "this", "to", "work"] >>= unlines >>= return  
  |                                          ^^^^^^^  

After figuring out what the error message tried to tell me, I got this working:

work :: String
work = ["Get", "this", "to", "work"] >>= (arr -> unlines [arr]) >>= return

main :: IO ()
main = putStrLn work

Question:
Why do I need to pass [arr] instead of arr to unlines?