Okay, I know it's because I'm dumb, but I still don't get it. Please don't yell at me, but why does the \K anchor keep .* from matching .jkl? And if it backtracks like normal, then where does the speed come from? I think that may be the essence of my confusion - why is this faster?

If I don't get it this time, I'll give up and just trust it ;-).

Light a man a fire, he's warm for a day. Catch a man on fire, and he's warm for the rest of his life. - Terry Pratchet