Creating your own programming language

Has anyone here every created their own programming language? What was the syntax like, and what did you use to implement the language? Using Haskell to implement your language is cheating BTW, so don't even post here if your language is made from Haskell.

Yo dawg I herd u like term substitution, so we put a lambda calculus in your lambda calculus so u can beta-reduct while u beta-reduct