Preferrably as patches (for example via git format-patch), as mail to perl5-porters@perl.org, or via the perlbug utility, which will send the mail for you. perlrepository (alternatively http://perl5.git.perl.org/perl.git/blob/HEAD:/pod/perlrepository.pod) has more information on how to set up a git mirror of bleadperl and how to format a patch but the basic workflow is:

1. git clone http://perl5.git.perl.org/perl.git bleadperl
2. Modify the document you want to modify, in your case, perlsub in pod/perlsub.pod
3. Commit your change(s) by using git commit -a -m "Make perlsub please LanX" or, better, a more descriptive name.
4. Create a patch file by using git format-patch origin - this should leave you with one (or more) files 0001-make-perlsub-please-lanx.patch, 0002-...
5. Send these to perl5-porters@perl.org, preferrably with a second description of your rationale behind creating the patch, and what the patch changes.