Man pages matching name bio::db::flat::bdb in section 3pm:

Bio::DB::Flat::BDB.3pm.en	debian 10 / libbio-perl-perl
Bio::DB::Flat::BDB.3pm.en	debian 11 / libbio-perl-perl
Bio::DB::Flat::BDB.3pm.en	debian 12 / libbio-perl-perl