Why don't you write such a browser and make it so good it displaces all the other common browsers out there now to become the leader of the pack that everything else follows?

This is not a question of open standards or anything of that sort, but of the historical growth of pretty much all the internet related technologies. The same sort of thing has happened many times in very many different areas. Consider Betamax and VHS for example or more recently Blu-ray Disc and HD DVD, or television video formats, or screw head types, or ... . Any place where there are trade offs affecting implementation and adoption that result in incompatible systems there tends to be a variant that succeeds and everything else falls by the wayside. That's just market forces at work and often has very little to do with the technical qualities of the technologies involved.

So all you have to do is convince all the browser suppliers and all web content providers that Perl should be the client side scripting language, or write a browser that is so much better than everything else that you can enforce your own will, and that particular part of the world is your oyster.