Probably, Module::CoreList is god-send as Andy Lester commented on CPAN ratings. It is always there (as long always is after 5.9.2 release or after you installed it from CPAN) to let you know since when you can rely on the availability of a certain core module. But I want to track the core module list while in development. I think this may occasionally be useful to developers and others paying attention to the evolution of the Perl interpreter.
So I got today a raw list of the core modules in bleadperl @ 26499, which can seen here: http://ferreira.nfshost.com/perl/corelist.html.