perl binding for C++ ref-counted object

Hi, everyone!I'm asking a question about how to wrapping a refcounted class inside perl.I have some experience on embedding perl in C++, but have little knowledge on perl XS, and I found perldoc perlxs really puzzled.Firstly, I have an simple refcounted C++ base class like this:class Referenced {public:    Referenced():refcnt(0) { }    virtual ~Referenced() {}    void refInc() { refcnt++; }    void refDec() {        if (--refcnt<=0) delete this;    }protected:    int refcnt;};In my wrapper, I want to have following functions:- able to construct my object within perl, like My::Class->new();- able to construct my object in C++, and pass it to perl sub as argument;- handle ref count correctly;So, is these things correct for my XS?Referenced::new(class)    PREINIT:        const char* class;        Referenced* obj;        SV* obj_wrap;        SV* sv;    CODE:        // create object        obj = new Referenced;        obj->refInc();                // store pointer as unsigned int?        obj_wrap = newSV(0);        sv_setuv(obj_wrap, (uv)obj);        // we always wrap 2 layers SVs for a class? Should I do these things manually?        sv = newSVrv(obj_wrap, class);        RETVAL = sv;    OUTPUT:        RETVAL// is this correct?// I don't really understand when would Perl do automatic scalar conversion, and when should I manually do that.Referenced::DESTROY(self)    PREINIT:        Referenced* self;    CODE:        self->refDec();