automounter -Dvariable=Value option?

The autofs(5) man page mentions that besides variables such as
ARCH, OSNAME "Additional entries can be defined with the
-Dvariable=Value option to automount(8).". How does that work?

I think it may be valuable in mounting different versions of
a tools directory. OSNAME is a very coarse granularity and OSREL
and OSNAME are way too fine. What I'd like to do is mount by
either RHEL3 or RHEL4 or perhaps a major-minor kernel rev,
something like 2.6-11.

Ernie