title: What does a dollar sign followed by a question mark mean in Perl?
body: <p>In the following in Perl script:</p>
  
  <pre><code>$a=apple
  $b=orange
  
  if ($?==0) {
    # do something
  }
  </code></pre>
  
  <p>What does <code>$?</code> mean here?</p>