Bison, flex and flow control

Hello!

The last month I am looking all over the internet for a tutorial on creating a simple scripting language with flow control (for, while, if) using bison and flex (or yacc and lex).

Can someone tell me the basic steps for doing that? I need desperately an answer or perhaps a link (if anyone knows one). The only resource I found was the book: “Unix Programming Environment” – Brian Kernighan and Rob Pike, but the book does not explain the code very well.

The scripting language I want to develop a very simple. I know how to manage variables (define them, assignment etc). I don't know how to implement FOR, IF and WHILE. In order not to confuse anyone, I am talking about a simple interpreter.

Thank you in advance,
Crashgr