varBind vn x = modify $ \(PegState s a w n c b p) ->
                            PegState s a w n c (M.insert vn x b) p
varBind vn x = modify $ \(PegState s a w n c b p) ->
                            PegState s a w n c (M.insert vn x b) p
varBind vn x = modify $ \(PegState s a w n c b p) ->
                            PegState s a w n c (M.insert vn x b) p