Man pages matching name device::gsm::pdu in section 3pm:

Device::Gsm::Pdu.3pm.en	debian 10 / libdevice-gsm-perl
Device::Gsm::Pdu.3pm.en	debian 11 / libdevice-gsm-perl
Device::Gsm::Pdu.3pm.en	debian 12 / libdevice-gsm-perl