Here is the code:

$("div").on("click",function(){
       console.log("click");
});
$("div").on("click.plugin", function(){
       console.log("click.plugin");
});
$("button").click(function() {
      $("div").trigger("click!");    
});

and the HTML:

<div>test.</div>
<button >Trigger event according to namespace</button>

When I [run the code under jQuery 1.8.3][1], it works. When I click button, it logs click in the console.

But when I [change to jQuery 1.9.1][2], nothing happens when I press the button. It seems like the exclamation mark doesn't work anymore in 1.9.1.

I can't find this change in the 1.9 upgrade guide. Does anybody know why?

[1]: http://jsfiddle.net/un9aP/

[2]: http://jsfiddle.net/un9aP/1/