Regex in Haskell patterns

Have you ever wanted to do case expr of regexhere -> ... ?
You can do almost that with view patterns!

{-# LANGUAGE ViewPatterns #-}

import Text.Regex.Posix

-- Helper
pat :: String -> String -> [[String]]
pat p s = s =~ p

-- Function with matching
foo :: String -> String
foo (pat "foo(bar|baz)" -> [[_,x]]) = x
foo _ = "no!"

main :: IO ()
main = do
  print $ foo "foobar"
  print $ foo "foobaz"
  print $ foo "yes?"

The above code will print bar baz no! . Have fun!