Do a clean upgrade on Gentoo

Because upgrade can be tricky to do (yeah Perl, I talk about you !)

eix-sync
emerge -Duva world
emerge --deselect --ask $(qlist -IC 'perl-core/*') &&
emerge -uD1a $(qlist -IC 'virtual/perl-*')
perl-cleaner --all or perl-cleaner --reallyall # depends how bad it looks
emerge --depclean
revdep-rebuild -v -- --ask
eclean-dist -d

Have fun !