During my project I was once at the point where I actually implemented my own (interpreted) scripting language. I have never thought that I'd be one of the guys who creates something like this, but once you are so fed up with something over the years (and I was with ESQL just for being "closed source") you'd just may be starting to go for it and just try out an dig into it.

And it works. I am now saying things like "If I'd need a JIT compiler for it, I'd write one. I'll look at everything and evaluate if possible and how to be done."

Inventing wheels is great for learning and I am now back to Java (good enough ;)