tcfail168.hs:7:11:
    Couldn't match expected type ‘IO a0’
                with actual type ‘Char -> IO ()’
    Probable cause: ‘putChar’ is applied to too few arguments
    In a stmt of a 'do' block: putChar
    In the expression:
      do { putChar;
           putChar 'a';
           putChar 'a';
           putChar 'a';
           .... }