Copy class-specific files?

[Kai Grossjohann]

I have a home-grown shell script to copy class-specific files.  What
does it mean to copy class-specific files?

Consider a master tree with three versions of /etc/foo: One version
for the machine quux, one version for laptops, and a default
version.  Then my copy script will use the quux version on the
machine quux, the laptop version on all machines that belong to the
laptops class, and the default version on all other machines.

The above can be hand-coded easily, but what I'm looking for is
something dynamic: if I decide that for the machine blarfl there
should be a fourth version of the file /etc/foo, then I just put an
appropriately-named file into the master tree, and the copy script
will pick that up automatically.

I'm sure that many people have this problem, so surely there must be
a real solution, instead of my home-grown script.

But where?

Kai