Can you suggest a powerful language or feature that supports modifying code in runtime?
This is what I mean by modifying code in runtime:
Start:
a=10,b=20,c=0;
label1: c=a+b;
....
label1= c=a*b;
goto label1;
and may be building a list of instructions:
code1.add(c=a+b);
code1.add(c=c*(c-1));
code1. execute();
Malbolge would be a good place to start. Every instruction is self-modifying, and it's a lot of fun(*) to play with.
(*) Disclaimer: May not actually be fun.