coreutils: PROG_PREFIX needs -, =, or _

[oech3]

$ ln -s /usr/bin/uu-coreutils /tmp/uu-true
$ /tmp/uu-true
$ ln -s /usr/bin/uu-coreutils /tmp/uutrue
$ /tmp/uutrue
uutrue 0.4.0 (multi-call binary)

Usage: uutrue [function [arguments...]]
...

I don't think soneone want to do that, but it should be documented if it is expected.

[oech3]

uu=true and uu_true is OK while uutrue does not work,

[oech3]

Since tty prefixed by s is stty, I think there is no effort more than doc.
@cakebaker Is there any idea to allow uutrue?