title: Does perl's -i with no argument create a backup file on Cygwin?
body: <p>I have a bug report from a reliable person that on Cygwin and Perl 5.14.2, using perl's <code>-i</code> switch with no value creates a <em>.bak</em> backup file. It shouldn't according to the documentation in <a href="http://perldoc.perl.org/perlrun.html" rel="noreferrer">perlrun</a>:</p>
  
  <pre><code>If no extension is supplied, no backup is made and the current
  file is overwritten.
  </code></pre>
  
  <p>I don't have access to Cygwin at the moment. Does anyone else see this behavior? Can you explain it? Is is something about creating the backup file, which should only be a temporary file, and failing to remove it?</p>
  
  <p>Here's the steps I suggest to recreate it. Remember, this is for Cygwin:</p>
  
  <ol>
  <li>Create and change into empty directory</li>
  <li>Create a text file in that directory. The contents are not important</li>
  <li>Run <code>perl -p -i -e 's/perl/Perl/g' filename</code></li>
  <li>Check for a <em>.bak</em> file when you are done</li>
  </ol>
  
  <p>Save the answers for an explanation of what might be happening if you find that backup file. Upvoting a prior comment for "Yes I see that" or "No, can't reproduce it" can be an informal poll.</p>