This was fixed in perl by commit
5988f306, in which Father Chrysostomos
says "CvNAMED should never be on after calling [CvGV_set], regardless
of the previous state of the CV".
#endif
CvGV_set(cv, gv);
+#if SU_RELEASE && SU_HAS_PERL_EXACT(5, 21, 4)
+ CvNAMED_off(cv);
+#endif
CvSTASH_set(cv, CvSTASH(proto));
/* Commit 4c74a7df, publicized with perl 5.13.3, began to add backrefs to
* stashes. CvSTASH_set() started to do it as well with commit c68d95645