Not only would CPAN need to compile the file, but also run it, as $VERSION is typically set at compile time. CPAN is not going to run the entire file.

What I'm trying to avoid is all the CPAN problems to which you allude: all the files in my package remain in lock step through every release (and reflect the version of the overall distribution).

Whether your files remain in lock step is not archieved by inheriting $VERSION. What you do lose is the ability to easily check whether your files are in lock step. If each file has its own $VERSION, it's easy to see if there's a mismatch. If they inherit from a single source, there's no way to find out.

IMO, if you inherit $VERSION, you'd lose one of major reasons to use a version number.

Abigail