>You could wrap this in a private function that returns the regex object. Use #[cfg(stage0)] to have it construct it at runtime and unwrap, and #[cfg(not(stage0))] to have it use the macro and a static.

It's not really a perf problem, just a nice to have, think it's worth adding this (minor) complexity?

> This regex is unnecessarily complicated. 

Yeah, I didn't really clean up the final version, mybad.