Hi, are Regex'es broken or is this local to my installation? I want to blame someone else, see: http://book.realworldhaskell.org/read/efficient-file-processing-regular-expr... where all result types of [a] are broken, too. Thanks, Christian What to test for: Prelude> :m Text.Regex.Posix Prelude Text.Regex.Posix> "aab" =~ "a" :: String "a" Prelude Text.Regex.Posix> "aab" =~ "a" :: [String] <interactive>:1:0: No instance for (RegexContext Regex [Char] [String]) arising from a use of `=~' at <interactive>:1:0-11 Possible fix: add an instance declaration for (RegexContext Regex [Char] [String]) In the expression: "aab" =~ "a" :: [String] In the definition of `it': it = "aab" =~ "a" :: [String]