This was the granddaddy package manager. Before gem or npm or maven or pip. It was the gold standard for sharing open source libraries and was the best reason for using Perl for a long time.
To be fair this was just a search engine for the package archive. The archive, it’s several clients, and alternative search engine, are still doing fine.
It still is. CPAN is not dead (although large parts of it are old cruft), they just changed the search engine for its web site.