wrote stvn thus:

When a module goes into the core it suddenly has a dual-life. There is the (frozen) version that is distributed with the latest version of perl, and then the (living) version that is on CPAN (you now, the one with the bugs fixed and new features).

Indeed! Would be nice to see a lean core, for if a bug happened to be in only the "core" version, then explicit work is needed to pick up the updated version (from a different path).