Noteworthy in the MRuby universe, which is all about lightweight Ruby implementations is picoruby. You can get an integrated ruby shell on a Raspberry Pi Pico:
It's something I ran into quite a few times in my career. It's a weird call to get if the client can't save their cms site, due to typing something harmless. I think worst was when there was a dropdown that I defined which had a value in the mod rules that was not allowed.
https://www.youtube.com/watch?v=WiJC_v5Lus8 https://picoruby.org/