title: What is an "illegal primary" in awk?
body: <p>Awk gives me the following error:</p>
  
  <pre><code>awk: illegal primary in regular expression (?&lt;=\&gt;)(.*?)(?=\&lt;) at &lt;=\&gt;)(.*?)(?=\&lt;)
  source line number 10 source file transpile.awk
  context is
      match($0, &gt;&gt;&gt;  /(?&lt;=\&gt;)(.*?)(?=\&lt;)/) &lt;&lt;&lt; 
  </code></pre>
  
  <p>But what <em>is</em> an "illegal primary"?</p>