Автозаполнение, появляющееся при вводе определенного символа

$(function() {
    var utilizatoriJson = [
        {'label': "@ActionScript",'id':'1'},
        {'label': "@Java",'id':'2'},
        {'label': "@C++",'id':'3'},
        {'label': "@Javascript",'id':'4'},
        {'label': "@Python",'id':'5'},
        {'label': "@BASIC",'id':'6'},
        {'label': "@ColdFusion",'id':'7'},
        {'label': "@Haskell",'id':'8'},
        {'label': "@Lisp",'id':'9'},
        {'label': "@Scala",'id':'10'}
    ];
    function split( val ) {
      return val.split( / \s*/ );
    }
    function extractLast( term ) {
      return split( term ).pop();
    }
 
    $( "#tags" )
      // don't navigate away from the field on tab when selecting an item
      .bind( "keydown", function( event ) {
        if ( event.keyCode === $.ui.keyCode.TAB &&
            $( this ).autocomplete( "instance" ).menu.active ) {
          event.preventDefault();
        }
      })
      .autocomplete({
        minLength: 1,
        source: function( request, response ) {
            // delegate back to autocomplete, but extract the last term
            var lastword = extractLast(request.term);
            if(lastword[0] != '@')
                return false;
            // Get all labels
            var labels = utilizatoriJson.map(function(item){return item.label;});
            response( $.ui.autocomplete.filter(
            labels, lastword ) );
        },
        focus: function() {
          // prevent value inserted on focus
          return false;
        },
        select: function( event, ui ) {
          var terms = split( this.value );
          // remove the current input
          terms.pop();
          // add the selected item
          terms.push( ui.item.value );
          // add placeholder to get the comma-and-space at the end
          terms.push( "" );
          this.value = terms.join( " " );
          return false;
        }
      });
  });

<link rel="stylesheet" href="http://code.jquery.com/ui/1.11.0/themes/smoothness/jquery-ui.css">

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script src="//code.jquery.com/ui/1.11.0/jquery-ui.js"></script>

<div class="ui-widget">
  <label for="tags">Tags: </label>
  <input id="tags" size="50">
</div>