title: I'd like to print the same line before every line with sed or awk
body: <p>I'd like to have a string inserted before 1st line and add them every other line.</p>
  
  <p>Before:  </p>
  
  <pre><code>a  
  b  
  c  
  d  
  </code></pre>
  
  <p>After:  </p>
  
  <pre><code>INSERT  
  a  
  INSERT  
  b  
  INSERT  
  c  
  INSERT  
  d  
  </code></pre>
  
  <p>Thanks in advance.</p>