Note: After saving, you have to bypass your browser's cache to see the changes. Internet Explorer: press Ctrl-F5, Mozilla: hold down Shift while clicking Reload (or press Ctrl-Shift-R), Opera/Konqueror: press F5, Safari: hold down Shift + Alt while clicking Reload, Chrome: hold down Shift while clicking Reload.
// purge tab$(function(){varhist;varurl;if(!(hist=document.getElementById('ca-history')))return;if(!(url=hist.getElementsByTagName('a')[0]))return;if(!(url=url.href))return;mw.util.addPortletLink('p-cactions',url.replace(/([?&]action=)history([&#]|$)/,'$1purge$2'),'purge','ca-purge','Purge server cache for this page','0');});