* Error: The above package list contains packages which cannot be
* installed at the same time on the same system.

(‘installed’, ‘/’, ‘perl-core/IO-Compress-Zlib-2.015′, ‘nomerge’) pulled in by
perl-core/IO-Compress-Zlib required by world

(‘ebuild’, ‘/’, ‘perl-core/IO-Compress-2.020′, ‘merge’) pulled in by
~perl-core/IO-Compress-2.020 required by (‘installed’, ‘/’, ‘perl-core/IO-Zlib-1.09′, ‘nomerge’)
~perl-core/IO-Compress-2.020 required by (‘ebuild’, ‘/’, ‘virtual/perl-Compress-Zlib-2.020′, ‘merge’)
~perl-core/IO-Compress-2.020 required by (‘ebuild’, ‘/’, ‘virtual/perl-IO-Compress-Base-2.020′, ‘merge’)
(and 5 more)

(‘installed’, ‘/’, ‘perl-core/Compress-Zlib-2.015′, ‘nomerge’) pulled in by
perl-core/Compress-Zlib required by world

Fortunately, after seeing this and having seen poppler doing the exact same, I knew the solution. Clearly perl-core/Compress-Zlib and perl-core/IO-Compress-Zlib were somehow present in world, while they should be mere dependencies.

The fix was just like last week’s fix:
emerge -C perl-core/Compress-Zlib perl-core/IO-Compress-Zlib

Easy does it! For more details, see the previous post.