title: Regular Expression - Validate a number
body: <p>I need to know how can I validate a number, but it's not any number, I need to validate this:</p>
  
  <p>If the number is <strong>0</strong> or if number is <strong>between 0.50 and 100</strong></p>
  
  <p>I can allow 0 and any other number (with or without decimals, if have, at max 2 decimals), but it has to be between 0.50 and 100.</p>
  
  <p>I've got this:</p>
  
  <pre><code>^[0-9]+\.?[0-9]*$
  </code></pre>
  
  <p>But it validates any number, and I can't do that.</p>
  
  <p>I need to validate it in a single expression, can someone help me?
  Thanks.</p>