I spent most of today updating from perl-5.22 to perl-5.24 because so many packages failed to install. I ran perl-cleaner about a hundred times and tried emerge -ac in between, which always failed because it falsely accused me of not doing emerge -auND.
Finally I got through the perl update and noticed a message saying 'emerge -auND --with-bdeps=y is the ultimate way to update...' so I added the '--with-bdeps=y' and another twenty perl-related packages got rebuilt after I thought I was done. Now I'm really done, I think, but I'm afraid to reboot this machine.

