I think Knuth did something similar before. TeX is written in WEB, which like that you can define many blocks and include them within other blocks, but it also has other features such as it will generate an index automatically.
I like the idea. Reminds me of the Eve language/IDE (www.witheve.com).
I can see why, Eve looks brilliant! It's pretty close to the way I would like to learn, develop and play with a program.