having #0 carry thru abstractions within abstractions

Hi all,
I know there is a way to do this (well I think there is), but I'm not having any luck finding it anywhere. Here's my story (it's a page turner):
you make an abstraction with say, "r #0_foo". When instantiated, #0 gets filled in by a randomly generated number. Now let's say this abstraction has within it another abstraction, with an "r #0_foo". Now for my purposes, I'd like both #0 to be the same within this little abstraction within an abstraction, but you get different numbers (and this is actually expected). BUT...I seem to recall somewhere in the dark recess of my brain a way of accomplishing this using "---" somwhere in place of, or next to, or on top of, #0. Then each of these abstraction-within-an-abstraction sets share same receive arguments, but data isn't shared across other similar abstraction-within-an-abstraction sets. Any combo I've come up with has proven fruitless, and doing a search for "---" or #(anything) doesn't produce any hits in the forum. Am I smokin' something? Is this possible? Certainly I have a workaround, but am looking to streamline some patches a bit.

Thanks in advance,
David