+void
+add(...)
+PROTOTYPE: @
+PREINIT:
+ HV *res;
+ SV *cur, *val;
+ HE *key, *old;
+ I32 i;
+CODE:
+ if (!items)
+ XSRETURN_UNDEF;
+ res = newHV();
+ for (i = 0; i < items; ++i) {
+ cur = ST(i);
+ if (!SvOK(cur))
+ continue;
+ if (!SvROK(cur)) {
+ if (strEQ(SvPV_nolen(cur), "list")) {
+ hv_clear(res);
+ val = newSVuv(1);
+ if (!hv_store(res, "list", 4, val, sn_hash_list))
+ SvREFCNT_dec(val);
+ break;
+ } else {
+ NV v = 1;
+ if ((old = hv_fetch_ent(res, cur, 1, 0)) && SvOK(val = HeVAL(old)))
+ v += SvNV(val);
+ val = newSVnv(v);
+ if (!hv_store_ent(res, cur, val, 0))
+ SvREFCNT_dec(val);
+ continue;
+ }
+ }
+ cur = SvRV(cur);
+ hv_iterinit((HV *) cur);
+ while (key = hv_iternext((HV *) cur)) {
+ SV *k = HeSVKEY_force(key);
+ NV v = SvNV(HeVAL(key));
+ if ((old = hv_fetch_ent(res, k, 1, 0)) && SvOK(val = HeVAL(old)))
+ v += SvNV(val);
+ val = newSVnv(v);
+ if (!hv_store_ent(res, k, val, 0))
+ SvREFCNT_dec(val);
+ }
+ }
+ if (!hv_iterinit(res)) {
+ SvREFCNT_dec(res);
+ XSRETURN_UNDEF;
+ }
+ ST(0) = sv_2mortal(newRV_noinc((SV *) res));
+ XSRETURN(1);
+