Maybe I really am less than competent, but as I see it, the Perl 5 core really had stagnated, development-wise, until it started borrowing features from Perl 6 -- features which wouldn't have existed if Perl 6 had pulled a Python 3000 and tried to make a few cosmetic changes and burn off a few warts here and there. (Proposing a patch to remove the Perl 1 style do subname notation starts vehement arguments on p5p, even though you can remove three percent of the entire Perl 5 parser by getting rid of a feature made obsolete at least sixteen years ago.)
Consider, as one example, the Perl testing revolution. Remember Test::Simple? Ever use Test::More? Like what Test::Builder has done for the Perl core, and CPAN, and CPANTS, and the quality of billions of lines of code written in the past eight years? Thank Perl 6 for that, because the Perl 6 QA working group decided that improving the test coverage and test tools and testing culture of Perl 5 was vital to the interest of making sure that Perl 5 and Perl 6 could interoperate.
Sure, you could claim that someone else would eventually have done something else, and that in that imaginary world things would be better, or more the sameish, or somewhat different, or everyone would wear a jaunty hat now, but facts are facts and history is history and anyone who was there will tell you that this is how it happened.
(Disclaimer: I know Moose has a lot of influences besides Perl 6, but so does the Perl 6 object system.)
(Second disclaimer: Perl 5 has grown immensely healthier in the past eight months, thanks in part to adopting yet another feature that Perl 6 and Parrot have demonstrated as useful -- the monthly release cycle. This is neither accident nor coincidence.)