title: Got `bad character range` in regex when using comma after dash but not reverse
body: <p>I have tried this command in python console:</p>
  
  <pre><code>re.match('^\&lt;.+\&gt;([\w\s-,]+)\&lt;.+\&gt;$', 'Carrier-A')
  </code></pre>
  
  <p>and I got:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/usr/lib/python2.7/re.py", line 141, in match
      return _compile(pattern, flags).match(string)
    File "/usr/lib/python2.7/re.py", line 251, in _compile
      raise error, v # invalid expression
  sre_constants.error: bad character range
  </code></pre>
  
  <p>but when I use:</p>
  
  <pre><code>re.match('^\&lt;.+\&gt;([\w\s,-]+)\&lt;.+\&gt;$', 'Carrier-A')
  </code></pre>
  
  <p>no error is being returned.</p>
  
  <p>What is it that I should consider about character sequences?</p>