Most CPAN mirrors take what PAUSE gives them. If an author deletes a file in his PAUSE account, that file disappears from the PAUSE master mirror and hence from the CPAN mirrors, by default. However, some people set up BackPANs; these are CPAN mirrors that don’t delete files. They maintain a near complete history of PAUSE uploads. Even if your files aren’t on CPAN, you can find them on BackPAN.
In rare circumstances, some mirrors remove files at the request of up loaders, usually when they mistakenly contained proprietary or confidential information. However, there’s no mechanism to remove those files from all mirrors since there is no one who regulates this. People have to track down each mirror operator on their own.