Install this version:
emerge -a =dev-perl/X11-Protocol-Other-31
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =dev-perl/X11-Protocol-Other-31
Or alternatively:
emerge --autounmask-write -a =dev-perl/X11-Protocol-Other-31
# Copyright 2021-2022 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
EAPI=8
DIST_AUTHOR="KRYDE"
inherit perl-module
DESCRIPTION="X11 Protocol related components not included in dev-perl/X11-Protocol"
LICENSE="GPL-3"
SLOT="0"
KEYWORDS="amd64 x86"
RDEPEND="dev-perl/X11-Protocol"
DEPEND="${RDEPEND}"
dev-perl/X11-Protocol
dev-perl/X11-Protocol