[plt-scheme] requiring specific identifiers

It would be nice if there were a `from' require specification, like so:

  (require (from "foo.scm" x y z))

In other words, I want the inverse of `all-except'.  (Maybe `just' is
a better name?)  As far as I can tell, the only way to do this
currently is like so:

  (require (rename "foo.scm" x x))
  (require (rename "foo.scm" y y))
  (require (rename "foo.scm" z z))

Let me know if I missed something in the docs.

--dougo at ccs.neu.edu