I did a cabal update then: cabal install regex-base cabal install regex-compat cabal install regex-posix Everything built and installed, there were no errors as far as I could tell. However, on attempting to get into regex on page 199 of my Real World Haskell book I get this error when trying to use [String] as the return type and I don't know why... GHCi, version 6.12.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. Prelude> :m Text.Regex.Posix Prelude Text.Regex.Posix> Prelude Text.Regex.Posix> "this is the string" =~ "th" :: [String] <interactive>:1:0: No instance for (RegexContext Regex [Char] [String]) arising from a use of `=~' at <interactive>:1:0-27 Possible fix: add an instance declaration for (RegexContext Regex [Char] [String]) In the expression: "this is the string" =~ "th" :: [String] In the definition of `it': it = "this is the string" =~ "th" :: [String] Prelude Text.Regex.Posix> I am trying to write a page scraper, I've already sucked pages with Network.HTTP and I thought it'd be easy to get the anchor tags!