I wrote it [0]. I meant to get it merged upstream, but the author took the repository offline to help build his business, so my fork bitrotted. However, it looks like Rust support may have independently landed upstream [2]?

[0]: https://github.com/erickt/ [1]: http://www.colm.net/news/2014/10/24/ragel-now-maintained-by-... [2]: http://www.colm.net/news/2015/09/26/first-dev-version-of-rag...