regex-applicative is a Haskell library for parsing using regular expressions. Parsers can be built using Applicative interface. Perl programmers often use regular expressions for parsing, even if it is not an appropriate tool for the job, because Perl has so good support for regexps. The opposite seems to be valid about Haskell programmers -- they use parsing combinators (which recognize context-free or even context-sensitive grammars), even when the language is actually regular! Hopefully, this library will improve the situation. After uninstalling, run this command to unregister the package from the ghc package database: ghc-pkg recache