The easiest way to create a Request is with the parseUrl function. This function will return a value in any Failure monad, such as Maybe or IO. The last of those is the most commonly used, and results in a runtime exception whenever an invalid URL is provided. However, you can use a different monad if, for example, you want to validate user input.

import Network.HTTP.Conduit
import System.Environment (getArgs)
import qualified Data.ByteString.Lazy as L
import Control.Monad.IO.Class (liftIO)

main :: IO ()
main = do
    args <- getArgs
    case args of
        [urlString] ->
            case parseUrl urlString of
                Nothing -> putStrLn "Sorry, invalid URL"
                Just req ->