[bjackman]

Piper is an extended reimplementation of Perforce

(Piper is piper, expanded recursively. It's so meta, even this acronym)

[steveklabnik]

And while it's not public, jj has a piper backend, so that folks at Google can use jj

(This is also why I have some confidence that jj truly is backend agnostic, it has two real backends already.)