[Haskell-beginners] hide Perl code inside Haskell program

I was trying to hide Perl code inside Haskell program like the following:

module Main where

import System.Environment (getArgs) import System.Cmd

main = do args <- getArgs rawSystem pl args where pl = "#!/usr/bin/perl\n" ++ "print \"testing ...\n\";"

The program can run, but generates no output at all. Can someone tell me any other tricks which might be missing? (Do we need to use pipe here?) Thanks, Hong