:: Ord a => [a] -> [a] is:exact -package:extra -package:statistics -package:ghc -package:imports -package:Cabal -package:lifted-base -package:safe -package:witherable -package:hxt -package:lens -package:basement package:parsers
Take a parser that may consume input, and on failure, go back to where
we started and fail as if we didn't consume input.