title: regular Expression to detect base64
body: <p>I read an article about a regular expression to detect base64 but when I try it in "yara python" it gives an error of "unterminated regular expression"
  the regular expression is: </p>
  
  <blockquote>
    <p>(?:[A-Za-z0-9+/]{4}){2,}(?:[A-Za-z0-9+/]{2}[AEIMQUYcgkosw048]=|[A-Za-z0-9+/][AQgw]==)</p>
  </blockquote>
  
  <p>could anyone throw a suggestion please?
  thanks</p>