I'd like to be able to give up on an STM transaction: roll back and don't retry. I've cooked up something with exceptions but it feels a bit icky to use exceptions for something like this - is there a better way?: data Rollback = Rollback deriving (Show) instance Exception Rollback rollback :: STM x rollback = throwSTM Rollback atomicallyWithRollback :: STM x -> IO (Maybe x) atomicallyWithRollback a = (Just <$> atomically a) `catch` (\Rollback -> pure Nothing) The alternative I've found is something like: otherWay :: STM x -> IO (Maybe x) otherWay a = atomically $ (Just <$> a) `orElse` pure Nothing But this turns any "retry" in "a" into a rollback, and I'd like to have the option to do either (retry or rollback). Thanks, Tom