title: Regex dismatch repeat special character
body: <p>I'm doing a regex to check a slug.
  Actually my regex is : <code>/^[^-][a-z\-].*[^-]+$/</code></p>
  
  <p>here's what I'm checking right now :</p>
  
  <p><code>my-awesome-project</code> => valid</p>
  
  <p><code>-my-awesome-project</code> => invalid</p>
  
  <p><code>my-awesome-project-</code> => invalid</p>
  
  <p>Now what I want is to check if the dash is repeating or not :</p>
  
  <p><code>my-awesome-project</code> => should be valid</p>
  
  <p><code>my-awesome--project</code> => should not be valid</p>
  
  <p><code>my----awesome-project</code> => should not be valid</p>
  
  <p>Can I do that with a regex ?</p>
  
  <p>Thank you,</p>