[thebiss]

For those of us that have never touched lisp - can you explain why?

[toolslive]

Lisp has quote, unquote, and friends allowing you to turn code into data, then manipulate it and then turn it back into code. These are all the tools you need to create on-the-fly compilers. Here's an article explaining the lost art:

http://gms.freeshell.org/peval.html