in reply to Code that writes code
Excellent topic! When I first saw this node, the first thing that came to my mind was compilers. Sure, they compile your programs to executables, but as anyone who's taken a compiler construction class knows, they can also work by generating code for a virtual machine (often some kind of stack machine), and then passing the generated code to a previously written implementation of the VM on the target machine (usually provided by the instructor, so you can concentrate on worrying about lexers and grammars and whatnot).
I used this approach in a Perl module implementation of The Dada Engine, which is a simple BNF-like grammar for writing out random text (example here). Instead of just writing a module that simply executes the grammar, the Perl port was written so that it translates the grammar to stack machine instructions. When these instructions are written out to an external file, along with the Perl implementation of that machine, you have a small and fast-running standalone script that outputs your random text.