Just stumbled across this fact.
All that you should have to do to make the licenses in META.yml/json appear as valid is add the line
LICENSE => 'perl'
To your Makefile.PL
( Assuming thats the license you want of course, based on the license description you put in the POD )
This is helpful for downstream consumers via the Metacpan api and populates the license: field on the left of this page:
Hope this helps =)
issue #11: add missing license metadata - thanks, kentfredric