Nothing real serious, but regenworld --help says your worldfile is in var/lib/portage/world. Perhaps this should be changed to the complete relative path : "/var/lib/portage/world".
Fixed in r9486 and released in sys-apps/portage-2.2_pre5.
This bug should be RESOLVED FIXED and block bug #210077.
This is supposed to be fixed in portage-2.2_pre5 or earlier.