title: Can regex match intersection between two regular expressions?
body: <p>Given several regular expressions, can we write a regular expressions which is equal to their intersection?</p>
  
  <p>For example, given two regular expressions <code>c[a-z][a-z]</code> and <code>[a-z][aeiou]t</code>, their intersection contains <code>cat</code> and <code>cut</code>  and possibly more. How can we write a regular expression for their intersection?</p>
  
  <p>Thanks.</p>