A few years ago Ragel was all the rage: http://zedshaw.com/archive/ragel-state-charts/

More or less. There was a minor parser combinator arms race in the Rust community a few months ago using http parsing as the benchmark and my takeaway (only half paid attention, I haven't needed to write a parser) was that they got to roughly as fast as handwritten C parsers. Example:

https://github.com/Geal/nom_benchmarks/tree/master/http

This hasn't translated into actual use in the Rust HTTP libs with hyper and rotor-http using their own handwritten parsers but I still think it might.

Yea, I'm not sure why that's a benefit, either. It's like they're trying to sell stuffed animals on Etsy, "hand sewed."