[smorrow]

The first paragraph of https://archive.org/details/rc-shell/

So rc was made for Plan 9. The examples in that paper are definitely on tenth edition Unix, I think this would be because

A fairly complete version of Plan 9 was built in 1987 and 1988, but development was abandoned. In May of 1989 work was begun on a completely new system

from https://doc.cat-v.org/plan_9/1st_edition/designing_plan_9 (1990).