title: Regex in TCL: Only allow numbers 0-9 and one special word
body: <p>I want to check the user input in a tablelist using a regex expression.
  Usually, I only want to allow digits <code>0-9</code> using this:</p>
  
  <pre><code>   $w configure -invalidcommand bell -validate key -validatecommand  {regexp {^[0-9]*$} %S}
  </code></pre>
  
  <p>It works fine. Now I want to extend this expression to only allow digits 0-9 or the exact word "Rigid". I tried this, but it allows me to type anything.</p>
  
  <pre><code>$w configure -invalidcommand bell -validate key -validatecommand  {regexp {regexp {^([0-9])|^Rigid?\&gt;*$} %S}
  </code></pre>