Vote +1 to add this to core. Please make coding in Perl 5 relatively painless.
experimental.pm doesn't do anything amazingly complex; it just eliminates the need for the rather annoying incantation:
no if ($] > 5.017011), warnings => "experimental::smartmatch";
... which is necessary to eliminate smartmatch-related warnings in Perl 5.18.
I'd been toying with an idea to release such a module myself, but thanks to LEONT I don't have to. Hurrah!