[racket] require url?

Hi all,

In the same way that it is possible to require a file given a local path:
eg.
(require (file "/home/..../foo.rkt"))

I'm looking for a way to require a file given a URL:
eg.
(require (url "http://tmp.barzilay.org/defmac.ss"))

The above does not work because url is not a require sub-form. file doesn't work either because it seems to convert the URL to a local path
("/http:/tmp.barzilay.org/defmac.rkt")

Is there a way to do that? 
I know that the best option is a planet package, but that's a bit heavyweight for my current needs.

Thanks,

-- Éric