PERL_CONTEXT *cx;
SV *sv;
- if (CxMULTICALL(&cxstack[cxstack_ix]))
+ if (CxMULTICALL(&cxstack[cxstack_ix])) {
+ /* entry zero of a stack is always PL_sv_undef, which
+ * simplifies converting a '()' return into undef in scalar context */
+ assert(PL_stack_sp > PL_stack_base || *PL_stack_base == &PL_sv_undef);
return 0;
+ }
POPBLOCK(cx,newpm);
cxstack_ix++; /* temporarily protect top context */