This probably would have been a nice excuse to implement reader macros and implement it that way, it's kinda a shame to have it implemented in the interpreter since most of the joy of Lisp is how much of the language can be written in the language itself.

Good suggestion, I'll look into it.

heist (https://github.com/jcoglan/heist) a lisp interpreter in ruby also supports string interpolation. however, i think this is a side effect of how they implemented string escaping. like you want to support \r\n\t, etc. if you send strings into Kernel#eval you get this for free :)