Replace file with url and you're in business

It'll do what the OP wants in the Mac OS X case, but isn't that just a side effect of the implementation of a specific HTML::Display subclass? Opening URLs doesn't appear to be part of the official API.

All the modules such as ... provide this which is what the author is after.

It won't work in all cases. For example HTML::Display::Win32::IE appears to push HTML straight to the browser from Perl. No filenames, let alone URLs involved.