[jQuery] Determining if form was submitted using jQuery

[neen]

Hi there,

I want to determine if a form has been submitted with jQuery or not.
I'm using the jQuery form plugin, but I need to degrade gracefully if
the user doesn't have JS enabled, so I want my function (server-side)
to return something different depending on whether the form was
submitted with AJAX or the old-school way.

Thanks!