Goals

Please keep in mind that we're reverse-engineering a spec, though, rather than designing in a vacuum.

We don't want everything that Module::Build can do, but we do want to stay as close as we can to what CPAN(PLUS|minus) (and possibly local::lib) already expect from the API.

I view it as "what the clients do now" plus "things they really ought to support" minus "crackpot ideas that they really shouldn't support".

An example of the latter was how they parsed files in the _build directory to find prereqs. That's been superseded by the MYMETA file mechanism, so the spec can omit anything related to _build/* files (and eventually CPAN clients can drop that parsing).