void
reduce(block,...)
    SV * block
PROTOTYPE: &@
CODE:
{
    SV *ret = sv_newmortal();
    int index;
    GV *agv,*bgv,*gv;
    HV *stash;
    SV **args = &PL_stack_base[ax];
    CV* cv    = sv_2cv(block, &stash, &gv, 0);

    if (cv == Nullcv) {
       croak("Not a subroutine reference");
    }

    if(items <= 1) {
	XSRETURN_UNDEF;
    }

    agv = gv_fetchpv("a", GV_ADD, SVt_PV);
    bgv = gv_fetchpv("b", GV_ADD, SVt_PV);
    ...