i have to assume the perl eclasses provide helpers to get these paths, but clearly hardcoding /usr/lib64/ is wrong, especially something stable on ppc/x86. exeinto /usr/lib64/perl5/vendor_perl/${PN^}/
from memory, please doublecheck: PERL_EXPORT_PHASE_FUNCTIONS=no inherit perl-module [...] perl_set_version exeinto "${VENDOR_LIB}/${PN^}/"
That ebuild had some more ugly problems. Fixed in -r2.