, withMVar -- :: MVar a -> (a -> IO b) -> IO b
, modifyMVar_ -- :: MVar a -> (a -> IO a) -> IO ()
, modifyMVar -- :: MVar a -> (a -> IO (a,b)) -> IO b
, withMVar -- :: MVar a -> (a -> IO b) -> IO b
, modifyMVar_ -- :: MVar a -> (a -> IO a) -> IO ()
, modifyMVar -- :: MVar a -> (a -> IO (a,b)) -> IO b