I almost got you what you were talking about ... and then I didn't. Your explanations are articulate, but I think you're talking from a place (a paradigm, dare I say it) that's a bit too foreign for us non-LISP people. How about if you wrote some code? That is, imagine some (hopefully small) example that uses this feature, without worrying about how it's implemented. And write it in "mostly-Perl", along with comments to help us see what's happening.

I wonder if tying variables, particularly scalars, could help in the implementation, but really I think I don't understand enough yet to comment usefully.