Man pages matching name exporter::declare::export::sub in section 3pm:

Exporter::Declare::Export::Sub.3pm.en	debian 10 / libexporter-declare-perl
Exporter::Declare::Export::Sub.3pm.en	debian 11 / libexporter-declare-perl
Exporter::Declare::Export::Sub.3pm.en	debian 12 / libexporter-declare-perl