updating file

[Jan Skibinski]

        Since we are in a mood for puzzles today ..

        How to update file "xxx" without
        making backup "yyy" first, as in:

                readFile  "xxx" >>=
                writeFile "yyy" >>=
                readFile  "yyy" >>=
                process         >>=
                writeFile "xxx"
        ?

        Jan Skibinski