RE: killring as registers

[Drew Adams]

> or asked the other way around: how do you use the killring and its
> history?

The standard way is to follow `C-y' with `M-y', repeating `M-y' to
cycle backward through the history to find the kill what you want.

There are a few libraries that give you other ways to yank past
kills than just cycling through the history.

One way:
https://www.emacswiki.org/emacs/BrowseKillRing

Another (using Icicles): `C-- C-y' or top-level `M-y' lets you yank
past kills using completion. You can filter or sort the candidates
on the fly.