极客大挑战 2019]RCE ME

给了源码，过滤了大小写数字，小于40长度
error_reporting(0);
if(isset($_GET['code'])){
            $code=$_GET['code'];
                    if(strlen($code)>40){
                                        die("This is too Long.");
                                                }
                    if(preg_match("/[A-Za-z0-9]+/",$code)){
                                        die("NO.");
                                                }
                    @eval($code);
}
else{
            highlight_file(__FILE__);
}
大部分都是采用的取反绕过