That way, if I want to install to a perl other than my default version, I could just invoke it with the full path name from wherever it lives

Actually, now that I think about it, that's exactly what I was doing at one point (and still getting the same error). At that time, the only perl in my path was the one that resides in MinGW/msys/bin - and I certainly don't want it getting invoked. (MinGW/msys/bin was in the path for other reasons, not because it contained a perl installation ... obviously.)

So, my guess at the reason for the route that Module::Build takes was probably a bad one.

Cheers,
Rob