title: Regular Expression to check for repeating characters
body: <p>I had to create a regular expression that allows in either the text "*ALL" (case independent) <em>OR</em> characters in the ranges a-z, A-Z and 0-9 which must be 17 characters long. This I have done without any problems:</p>
  
  <pre><code>^([\*][Aa][Ll][Ll]|[a-zA-Z0-9]{17})$
  </code></pre>
  
  <p>The problem I am having is how to alter it so that it picks up if just the same character is entered a number of times (e.g. 17 x's). </p>