Challenge 1: A First Two-Line Program — Possible Solution
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Main.hs:

main :: IO ()
main = do
  putStrLn "Hello from Haskell!"
  putStrLn "This is my second line."

Terminal:

    $ runghc Main.hs

Output:

    Hello from Haskell!
    This is my second line.

Explanation:
main's type signature, IO (), states directly that this computation
performs IO and produces no meaningful result. Since main now needs
to run TWO actions in sequence, it uses a `do` block -- syntax for
sequencing IO actions -- with each putStrLn call on its own line.
runghc compiles the file in memory and runs it immediately, without a
separate explicit compile step.

WHY THIS WORKS AS AN ANSWER
------------------------------
This uses the chapter's own main :: IO () shape, extended with a do
block to sequence two putStrLn calls, and runs it with runghc exactly
as the chapter demonstrates.