At its simplest, the CPAN is a bunch of files and an index. The index directs you from package names to the files that contain the latest authorized release of that package. Everything else builds on top of that.
If you want to publish Foo::Bar to the CPAN, you need to use PAUSE. PAUSE manages users and permissions, authenticates users, accepts uploads, and then decides how and whether to index them. To make those indexing decisions, first PAUSE analyzes an uploaded file to see what packages it contains. Then it compares those packages to the permissions of the uploading user. If the user has permission, and if the uploaded package is later-versioned than the existing indexed package, the package is indexed.
I have skipped some details, but I believe that for the purpose of everything else I'm going to write about, this is a sufficient explanation.
To get permissions on a package that isn't indexed at all, you upload it. Then you have permissions. If you want to work with a package that already exists, the person who uploaded it needs to give you permission. There are two kinds of permission:
When you view code on MetaCPAN or search.cpan.org, one of the most visible details is the name (and avatar) of the last user to have uploaded that package. This creates a strong impression that this is the contact point for the package. Sometimes, this is true, or true enough. On the other hand, sometimes it's not, and that's a problem. It may be that the last person to upload the library only did so as a one-off act, or that they were a member of the team working on a project years ago when it was last released. Now, though, they will be boldly listed as the contact person.
Here's a scenario:
Bob can't just pass on permissions to stop it. He can give up permissions, but he'll still be the last uploader.
You might object: "Alice should have given Bob first-come! Then he could pass along permissions!"
This is true. Maybe in 2010, Bob gives permissions to Charlotte... but now Charlotte is stuck in the same position. If nobody ever comes along to take it over, Charlotte can't usefully get out from under the distribution.
In 2013, the QA Hackathon led to a consensus about a mechanism for permission transitions. It goes something like this:
(The third magic user, "NEEDHELP," is not relevant to the topic at hand.)
Marking a library with ADOPTME or HANDOFF is useful in theory, but not in practice, because it's almost impossible to know that it has happened. Yesterday, I filed a bug about making ADOPTME/HANDOFF visible on MetaCPAN, and I think it's critically important to making the ADOPTME/HANDOFF worth having.
So, why is this section headed "half a solution"?
Because this solution helps you if you have first-come, but not if you have co-maint. Imagine poor Bob, above, in 2016. By this point, Alice has moved off the grid and can't be contacted. Bob can't mark the dist as ADOPTME. He can ask the PAUSE admins to do so, but that's it. It's also a bit a burden to put onto the PAUSE admins, who may not know whether Bob has really made a good faith effort to contact Alice.
The final remaining problem is this: There is no escape hatch for someone who has co-maint permissions and wants to get out from under the shadow of an unwanted upload.
This problem could be solved by adding a "GitHub Organizations"-like layer to PAUSE… but I think there's a much, much simpler mechanism.
We should always treat the first-come owner as the authoritative source, including when displaying a distribution on the web. MetaCPAN Web should stop showing the name and image of the latest uploder as prominently, and should show the first-come user instead. The same goes for search.cpan.org and other such sites. MetaCPAN already has a place for listing other contributors, which should contain the last uploader. Adding note like "last upload by BOB" seems okay, too, but the emphasis should be on connecting the distribution with the one person who can actually make decisions about its future.