Safely wrap jQuery when multiple versions are present on a page

gistfile1.html

<!--
For testing how multiple versions of jQuery interact on a page, 
 see http://jsfiddle.net/dalesaurus/5TgkG/
-->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript">window.jQuery || document.write('<script src="/js/jquery-1.7.1.min.js"><\/script>')</script></script>
<script type="text/javascript">
	var jQuery171 = window.jQuery;
	jQuery171(document).ready(function($){
		// Do work, son!
	})(jQuery171);
</script>