appendStack x = modify (\(PegState s a w n c b p) -> PegState (x++s) a w n c b p)
appendStack x = modify (\(PegState s a w n c b p) -> PegState (x++s) a w n c b p)
appendStack x = modify (\(PegState s a w n c b p) -> PegState (x++s) a w n c b p)