Expanded read list on the same topic:

http://www.ncameron.org/blog/sets-of-scopes-macro-hygiene/

https://github.com/acarrico/evaluator

Rust plans to switch to sets of scopes algorithm for macros: http://www.ncameron.org/blog/sets-of-scopes-macro-hygiene/

Whenever I see racket I like to point out their very awesome quick start guide:

https://docs.racket-lang.org/quick/

Also, relevant here is a quick build-your-own-language tutorial for racket at beautifulracket:

http://beautifulracket.com/stacker/intro.html

Worth it - both excellent resources.

Utah represent!