Besides that doing `perl -e 'for (;;) {}'` and watching your OS burn down in flames (which it doesn't) is the correct parallel, I'll assume you have overlooked that we have no control on what JS does in whatever page we're presented with, and if it's some heavy handed code it has a significant impact on whatever else I may be doing on an unrelated tab, which feels like going back to plain old cooperative multitasking, upon which the above perl code would effectively be a blight.