Man pages matching name message::passing::filter::regexp in section 3pm:

Message::Passing::Filter::Regexp.3pm.en	debian 10 / libmessage-passing-filter-regexp-perl
Message::Passing::Filter::Regexp.3pm.en	debian 11 / libmessage-passing-filter-regexp-perl
Message::Passing::Filter::Regexp.3pm.en	debian 12 / libmessage-passing-filter-regexp-perl