Man pages matching name net::ldns::rr::mx in section 3pm:

Net::LDNS::RR::MX.3pm.en	debian 10 / libnet-ldns-perl
Net::LDNS::RR::MX.3pm.en	debian 11 / libnet-ldns-perl
Net::LDNS::RR::MX.3pm.en	debian 12 / libnet-ldns-perl