So first they take monolithic code and modularize it. Then they bundle it back into a single piece of code. Then they do this:

  <script id="lazy">
  // Make sure you strip out (or replace) comment blocks in your JavaScript first.
  /*
  JavaScript of lazy module
  */
  </script>

  <script>
  function lazyLoad() {
    var lazyElement = document.getElementById('lazy');
    var lazyElementBody = lazyElement.innerHTML;
    var jsCode = stripOutCommentBlock(lazyElementBody);
    eval(jsCode);
  }
  </script>

What if my JavaScript code looks like this:

var x = "hello /* world */";

I wouldn't do it this way. Instead just bundle all your code into a single file and optimize its caching. No HTML5 needed: use HTTP headers.