:: Ord a => [a] -> [a] -package:list-t -package:extra -package:errors -package:imports -package:lifted-base -package:ghc -package:base -package:basement is:exact -package:amazonka-core -package:mono-traversable -package:containers 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.