title: What does dot-equals mean in Perl?
body: <p>What does ".=" mean in Perl (dot-equals)?  Example code below (in the while clause):</p>
  
  <pre><code>if( my $file = shift @ARGV ) {
      $parser-&gt;parse( Source =&gt; {SystemId =&gt; $file} );
  } else {
      my $input = "";
      while( &lt;STDIN&gt; ) { $input .= $_; }
      $parser-&gt;parse( Source =&gt; {String =&gt; $input} );
  }
  exit;
  </code></pre>
  
  <p>Thanks for any insight.</p>