> I think this was discussed on the p5p list - this XS interface was
> changed or removed in 5.21.1.

from Reini Urban's p5p message:

bless does not inc PL_sv_objcount since 5.17.11 anymore and does global destruction without checking for PL_sv_objcount, which slows down global destruction in the case of small scripts without any blessed objects.
               
5.21 removed now the variable at all, so that's why you get this error only now.
But it was effectively unused since 5.18.             


--- ./Guard.xs~ 2009-07-18 23:58:41.000000000 -0500
+++ ./Guard.xs  2014-06-27 10:18:45.821008691 -0500
@@ -110,7 +110,9 @@                                                     
         sv_magicext (guard, cv, PERL_MAGIC_ext, &guard_vtbl, 0, 0);
         RETVAL = newRV_noinc (guard);
         SvOBJECT_on (guard);
+#if PERL_VERSION < 18
         ++PL_sv_objcount;
+#endif                                            
         SvSTASH_set (guard, (HV*)SvREFCNT_inc ((SV *)guard_stash));
 }
        OUTPUT: