Man pages matching name http::proxy::headerfilter::standard in section 3pm:

HTTP::Proxy::HeaderFilter::standard.3pm.en	debian 10 / libhttp-proxy-perl
HTTP::Proxy::HeaderFilter::standard.3pm.en	debian 11 / libhttp-proxy-perl
HTTP::Proxy::HeaderFilter::standard.3pm.en	debian 12 / libhttp-proxy-perl