I don't know what 'upgrade' is supposed to do and, after seeing all that garbage that it threw at you, it's very unlikely that I'll ever try testing it for myself.
The most recent version "1.12" of the module "warnings"
is part of the perl-5.15.4 distribution.
That's just bullshit - perl-5.16.0 ships with version 1.13 of warnings. And the implication that you should install 5.15.4 is plain ludicrous.
What are you trying to achieve ? Maybe there's a better way