Ebuild is missing GENTOO_DEPEND_ON_PERL="no", see perl-module.eclass
Created attachment 361986 [details, diff] patch Attached trivial patch, works fine here.
Sorry for the delay. looks good to me (patch included)
+ 24 Nov 2013; Sergey Popov <pinkbyte@gentoo.org> collectd-5.1.0-r1.ebuild, + collectd-5.1.0-r2.ebuild, collectd-5.1.1.ebuild, collectd-5.1.1-r1.ebuild, + collectd-5.2.0.ebuild, collectd-5.2.0-r1.ebuild, collectd-5.2.1.ebuild, + collectd-5.2.2.ebuild, collectd-5.3.0.ebuild, collectd-5.4.0.ebuild: + Package should not depend on dev-lang/perl unconditionally, bug #487406. + Thanks to Nikoli <nikoli AT gmx.us> for discovering this issue