void
func(doublearrsv)
    SV * doublearrsv
PREINIT:
    STRLEN len;
    double (*doublearr)[3];//I hope this works
CODE:
    doublearr = SvPV(doublearrsv, len);//cast warning here
    if(len != sizeof(*doublearr)) croak("bad len");
    do_nothing(&doublearr[2]); //THIS WILL UPDATE IN PERL LAND