Man pages matching name net::sip::dropper::byfield in section 3pm:

Net::SIP::Dropper::ByField.3pm.en	debian 10 / libnet-sip-perl
Net::SIP::Dropper::ByField.3pm.en	debian 11 / libnet-sip-perl
Net::SIP::Dropper::ByField.3pm.en	debian 12 / libnet-sip-perl