The way in which code is modified in Lisp is generally in the source code itself, and overtly in the run-time environment or binaries. The latter might be what

The way in which code is modified in Lisp is generally in the source code itself, and overtly in the run-time environment or binaries. The latter might be what you're alluding to. Allowing code to be treated as data is a very powerful thing when it comes to programming. But of course, with more power there is more danger.