title: Obtaining overlapping matches using a regex
body: <p>See code first plz~ </p>
  
  <p>This is perl code.</p>
  
  <pre><code>my $st = 'aaaa';
  
  while ( $st =~ /aa/g ) {
      print $&amp;, "\n";
  }
  </code></pre>
  
  <p>I want to move one point of the string. </p>
  
  <p>So I want the results of the three <code>aa</code>. </p>
  
  <p>However, only two results are obtained. </p>
  
  <p>I can derive three results do?</p>