Man pages matching name bio::matrix::psm::sitematrix in section 3pm:

Bio::Matrix::PSM::SiteMatrix.3pm.en	debian 10 / libbio-perl-perl
Bio::Matrix::PSM::SiteMatrix.3pm.en	debian 11 / libbio-perl-perl
Bio::Matrix::PSM::SiteMatrix.3pm.en	debian 12 / libbio-perl-perl