portmaster display inclusion logic

Is there a way to cause portmaster -a to display it's logic for adding ports?

Specifically, I have a system with perl5-5.20.3_8 already installed, but running portmaster -a stipulates that lang/perl5.22 should be installed. This, of course, fails due to conflict.

Presumably another port I'm upgrading wants 5.22 instead of 5.20? How might I most easily determine which port has special requirements?
Well, I figured out that 5.22 was being required because I recycled a make.conf from another machine.

However, my original question still stands: is there some way to display the dependency logic?