Surely all of this complex parsing logic must come at a pretty hefty price.
Well, no, I wouldn’t say that.
This post is about specific backtracking scenarios that can cause exponential behavior. It’s not very common. But if it happens the results can be quite painful.
Also the hotmail devs are writing code that probably gets 10,000 times more pressure under use than anything we’ll ever write. So keep that in mind, too.