i have this code:

<script>
$("#mod").change(function() {
 var matches=str.match(/(EE|[EJU]).*(D)/i);
         $.ajax({
                  type="post",
                  url="process.php",
                  data="matches",
                  cache=false,
                  async=false,
                  success= function(res){
                                                                                 $('#rslt').replaceWith("<div id='value'><h6>Tuner range is" + res + " .</h6></div>");
   return this;
                              }
                        });
   return false;
});
 </script>

i want this code can show the result normally..where is my fault?