title: Lookahead confusion
body: <p>Ok i got this example from Regular Expression Cookbook</p>
  
  <pre><code>^(?=.{3}$).*
  </code></pre>
  
  <p>The regex above is use to limit the length of an arbitrary pattern</p>
  
  <p>If i test again 'aaabbb', it completely fail</p>
  
  <p>From what i understand it look for any character that precede by any character 3 in length.SO it should match 'bbb' but its not</p>
  
  <p>One more question, should lookbehind follow this pattern x(?=x)</p>