Man pages matching name git::raw::odb::backend::onepack in section 3pm:

Git::Raw::Odb::Backend::OnePack.3pm.en	debian 10 / libgit-raw-perl
Git::Raw::Odb::Backend::OnePack.3pm.en	debian 11 / libgit-raw-perl
Git::Raw::Odb::Backend::OnePack.3pm.en	debian 12 / libgit-raw-perl