:: Ord a => [a] -> [a] -package:html-entities -package:ghc -is:exact -package:lens -package:vector-algorithms -package:mono-traversable -is:exact -package:witherable -package:safe -package:base -package:containers -package:errors 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.