Q: in there a function that can find a file or open a URL as needed?

I have a string that can be either a) a local filename, or b) a URL. Is there an existing function that I can call on the string that will do what I mean and open the file if it's a file, or open the URL in a browser if it's a URL?

It wouldn't be hard to write such a function, but I'd rather not reinvent the wheel.