override-xhr.js

(function() {

   var oldXhr = dojo.xhr;

   dojo.xhr = function(/*String*/ method, /*dojo.__Scrags*/ args,
     /*Boolean?*/ hasBody){
     // first clone so we don't screw up original caller
     var cloneargs = dojo.mixin( {}, args );
     if (cloneargs.url) {
       cloneargs.url = 'myfunkyurl?a=' + cloneargs.url;
     }
	 return oldXhr.apply( dojo, [ method, cloneargs, hasBody]);
   };

 })();