Erik asked:

> does anyone with a 2e licence know if plumber used to accept rules
> like this; that is shell script fragments?

It did not - because the plumber did not exist in 2e or earlier. Like
a handful of other things, it was originally drafted for Inferno and
then backported (with improvements) to Plan 9.

Looking at my current Inferno rules, they look like the rules we see
in Plan 9. I've not looked beyond my own rules to see if they accept
the other style.