--
-- Extending the atomicity to multiple 'IORef's is problematic, so it
-- is recommended that if you need to do anything more complicated
--- then using 'MVar' instead is a good idea.
+-- then using 'Control.Concurrent.MVar.MVar' instead is a good idea.
--
atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
#if defined(__GLASGOW_HASKELL__)