regex" class. You can see an example of doing just that on my quick and dirty test page.
\10 is backreference 10, backreference 1 followed by a literal zero, octal character index 10, or something else altogether due to its position in the surrounding pattern. Speaking of octal escapes (which are de facto browser extensions; not part of the spec.), they are correctly highlighted according to their subtle differences inside and outside character classes (outside of character classes only, octals can include a fourth digit if the leading digit is a zero).
title attributes for each element in the returned HTML, which might be particularly helpful for deciphering any highlighted errors or warnings.
Let me know if this library is useful for you, or if there are any other features you'd like to see added or changed. Thanks!