In stage builds:

!!! The following update has been skipped due to unsatisfied dependencies:

virtual/perl-Perl-OSType:0

emerge: there are no ebuilds to satisfy "=dev-lang/perl-5.20*".
(dependency required by "virtual/perl-Perl-OSType-1.7.0" [ebuild])

In perl-Perl-OSType-1.7.0:

RDEPEND="
        || ( =dev-lang/perl-5.20* ~perl-core/${PN#perl-}-${PV} )
...

Or in other words, perl-5.20 or perl-core/perl-OSType-1.7.0, which doesn't exist.

Workaround until fixed upstream would be to mask this ebuild.