When you use the MetaCPAN API to search for that module (https://fastapi.metacpan.org/v1/module/DBD) it returns the distribution HDB because its HDB::MOD package contains a package DBD, so the CPAN indexer picked that up. I think it probably would have been better if the module's author had set that up so that that package didn't get indexed, but that's the way it is at the moment.