{
    my $static_var = 0;
    sub return_op {
        say "in return_op: $static_var";
        return $static_var;
    }
}

##</code><code>##

int main(.......) {
    ......
    // return value test
    {
        cout<<"### return value test"<<endl;        
        pppStack re1 = interp->call("return_op",true,false);
        pppStack re2 = interp->call("return_op",true,false);
    }
    ,,,,,,
}

##</code><code>##

class pppInterp
{
public:
    ......// a lot of methods here

    pppStack call(string subname, bool want_re, bool want_array);
    pppStack call(string subname, pppStack& args, bool want_re, bool want_array);

protected:
    // the interpreter only has this one property
    static bool inited;
    PerlInterpreter* my_perl;
}

//
// the method implementation
//

pppStack pppInterp::call(string subname, bool want_re, bool want_array)
{
    pppStack empty;
    return call(subname,empty,want_re,want_array);
}

pppStack pppInterp::call(string subname, pppStack& args, bool want_re, bool want_array)
{
    // enter sub
    SPAGAIN;
    ENTER;
    SAVETMPS;

    // push args
    PUSHMARK(SP);
    pppStack::iterator it;
    int arg_count = 0;

    for (it=args.begin(); it!=args.end(); it++) {
        SV* arg_copy = newSVsv((*it)->get_internal());
        sv_2mortal(arg_copy);
        XPUSHs(arg_copy);
        arg_count++;
    }

    PUTBACK;

    // call sub
    I32 flags = G_EVAL;
    if (arg_count==0) flags |= G_NOARGS;
    if (!want_re)     flags |= G_DISCARD;

    if (want_array) flags |= G_ARRAY;
    else            flags |= G_SCALAR;

    int re_count = call_pv(subname.c_str(),flags);

    // check eval
    if (SvTRUE(ERRSV)) {
        if (want_array) POPs;
        throw(SvPV_nolen(ERRSV));
    }

    // fetch args
    pppStack re;

    if (want_re) {
        SPAGAIN;
        int i;
        for (i=0; i<re_count; i++) {
            SV* tmp = POPs;
            Perl_sv_dump(my_perl,tmp);
            re.push_front( create_sv(tmp) );
        }
    }

    PUTBACK;

    // exit sub
    FREETMPS;
    LEAVE;

    return re;
}


##</code><code>##

### return value test
in return_op: 0
SV = PVIV(0xffd228) at 0xfebda0
  REFCNT = 1
  FLAGS = (TEMP,IOK,POK,pIOK,pPOK)
  IV = 0
  PV = 0x1013fd0 "0"\0
  CUR = 1
  LEN = 8
in return_op: 0
SV = PVIV(0xffd240) at 0xfebf80
  REFCNT = 1
  FLAGS = (TEMP,IOK,POK,pIOK,pPOK)
  IV = 0
  PV = 0x10102b0 "0"\0
  CUR = 1
  LEN = 8