yieldmo

var addScriptTag =  function(url) {
  var node = document.createElement('script');
  node.type = 'text/javascript';
  node.async = true;
  node.src = ('https:' === document.location.protocol ? 'https:' : 'http:') + url;
  node.id = '' + new Date().getTime();
  var topelem = (document.getElementsByTagName('head')[0] ||
                 document.getElementsByTagName('body')[0]);
  topelem.appendChild(node);
};

yieldmo

<form method="post" 
      action="https://...some/form/action" 
      name="signup" 
      id="sadf22222" 
      accept-charset="UTF-8" 
      onsubmit="return verifyForm();" >
<input type="hidden" 
       class="ym_tag_with_click" 
       name="redirect" 
       value="http://example.com/trackme/yay/">

yieldmo

// this could be minified by their build system
//
(function(window,document){
  var tokenizer = function(key, searchString) {
    var result = new RegExp(key + "=([^&]*)", "i").exec(searchString || window.location.search);
    return result && unescape(result[1]) || "";
  };
  var clickId = tokenizer('click_id');
  if(!clickId || clickId.length < 1){
    return;