title: ack regex: Matching two words in order in the same line
body: <p>I would like to find lines in files that include two words, <code>word_1</code> and <code>word_2</code> in order, such as in <code>Line A</code> below, but not as in <code>Line B</code> or <code>Line C</code>:</p>
  
  <pre><code>Line A: ... word_1 .... word_2 .... 
  Line B: ... word_1 ....
  Line C: ... word_2 ....
  </code></pre>
  
  <p>I have tried</p>
  
  <pre><code>$ack '*word_1*word_2'
  $ack '(word_1)+*(word_2)+'
  </code></pre>
  
  <p>and the same commands with <code>^</code> appended at the beginning of the regex (in an attempt to follow the Perl regex syntax).</p>
  
  <p>None of these commands return the files or the lines I am interested in.</p>
  
  <p>What am I doing wrong?</p>
  
  <p>Thanks!</p>