title: Replace a variable in a String
body: <p>I am looking for a String Utils so that I can do something like this.</p>
  
  <pre><code>String input = "this is the $var on $date"
  someUtil.evaluate(input, [var: "end", date: "11/11/11"])
  </code></pre>
  
  <p>output : this is the end on 11/11/11.</p>
  
  <pre><code>someUtil.evaluate(input, [var: "start", date: "10/10/10"])
  </code></pre>
  
  <p>output : this is the start on 10/10/10.</p>