Hello, While occasionally and slowly updating the future version of regex-tdfa I found a bug that exists in the released 1.1.1 version. It was just a matter of passing the wrong value into a function, so was easy to fix when I figured it out. The test case triggered an impossible "error" call and so I know this can kill a program that uses a buggy version of this library. Please upgrade regex-tdfa to version 1.1.2 which is available on hackage at: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/regex-tdfa Cheers, Chris