Really, with Perl the distinction "part of the core language" is meaningless. You can install a CPAN bundle for a hardcore Perl in one shell command, or get it all preinstalled. Strawberry Perl for Windows has all the good stuff in a single installer, for instance, and if you're on Unix you've similarly got no excuse.

Really. "Core language" is kind of twentieth. Moose is very well-established in the Perl community. That's as core as it gets.