:: Ord a => [a] -> [a] -package:html-entities -package:base-prelude -is:exact -package:safe -package:lens -package:containers -package:lifted-base -package:extra -package:basement -package:amazonka-core -package:errors package:parsers -is:exact
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.