Add a META.yml to the distribution. Your buildtool should be able to autogenerate it.
Add a README to the distribution. It should contain a quick description of your module and how to install it.
Add =head1 LICENSE and/or the proper text of the well-known license to the main module in your code.
Add a META.json to the distribution. Your buildtool should be able to autogenerate it.
Add tests or move tests.pl to the t/ directory!
Define the license if you are using in Build.PL. If you are using MakeMaker (Makefile.PL) you should upgrade to ExtUtils::MakeMaker version 6.31.
Add 'use warnings' (or its equivalents) to all modules (this will require perl > 5.6), or convince us that your favorite module is well-known enough and people can easily see the modules warn when something bad happens.
This is not a critical issue. Currently mainly informative for the CPANTS authors. It might be removed later.