Why would anyone be interested in an old regex package that never was a part of any Unix distro? The driving force was Posix, whose regex spec was quite inscrutable. Could there be a reference implementation? It was easy to fool every implementation I could get my hands on, including Gnu's over-the-top 9000-line implementation. But as I got into it, I got fascinated by regexes per se. In making a recognizer, there's a tradeoff between contruction time and execution time. Linear execution can be achieved, but at a potentially exponential cost in construction time (and space). Backreferencing takes the regex languages out of the class of regular languages. Recalling that regular languages are closed under intersection and negation, I wondered about how to implement new regex operators, & and -. I came up with a scheme for this optional non-Posix feature that involved layering continuation-passing over more traditional methods. And while I was at it, I broke out smaller sublanguages for special treatment (as does Gnu), all the way down to Knuth-Morris-Pratt for expressions in which the only operation is catenation. And finally, having followed the development of C++ from its infancy, I wanted to try out its new template facility, so there's a bit of that in the package, too. Arnold has discovered that not only has C++ evolved, but also that without the discipline of -Wall to force clean code, I was rather cavalier about casting, both explicitly and implicitly. The only real customer the code ever had was the AST project, which translated it to C. After the C++ had sat idle for a half-dozen years, I thought to revive it in Linux, but found it riddled with incompatibilities with that new environment and gave up. Arnold deserves a citation for bravery in pushing that through 15 years further on. Doug