Cleaning up after "@"-abort

• Use try{}/finally{} to clean up, release acquired resources, etc..
• Just like for exceptions, finally-block will always be executed, no matter if code in try-block exits normally or if it is aborted.

      function alert(message) {
        try {
          var messagebox = document.createElement("div");
          messagebox.setAttribute("style",  
                    "border: 2px solid red;width:200px;text-align:center;padding:10px;");
          messagebox.innerHTML = "<div>"+message+"</div>" +
                                 "<button>Dismiss</button>";
          document.getElementById("playpen").appendChild(messagebox);
          Ajax.DOM.waitForEvent("click", messagebox.lastChild);
        }
        finally {
          messagebox.parentNode.removeChild(messagebox);
        }
      }

      alert("Hello, world!") @ hold(10000);