Man pages matching name sgml::parser::opensp in section 3pm:

SGML::Parser::OpenSP.3pm.en	debian 10 / libsgml-parser-opensp-perl
SGML::Parser::OpenSP.3pm.en	debian 11 / libsgml-parser-opensp-perl
SGML::Parser::OpenSP.3pm.en	debian 12 / libsgml-parser-opensp-perl