I was first made aware of this Ragel project when _why was still around and he announced the hpricot html parser. https://www.ruby-forum.com/t/hpricot-0-1-quick-cinchy-html-p... I really looked upon him (and Zed too for the mongrel project).

His parser was built around xpath/css-selectors and it blew my mind at the time. I was interning at a company that built hundreds of web scrapers around regexes, Perl 5 and some other in-house DSL. I was wrapping up my university classes on theory of computation and compilers. Although I never made a career in that field, this was perfect timing and it allowed me to connect the dots. One day, I introduced the more senior employees to the limitations of regexes, capabilities that an html parser could bring to our projects as well as some freshly learned theory of context free grammars :P https://en.wikipedia.org/wiki/Chomsky_hierarchy