title: Shell variable visible in double quoted Perl one-liner
body: <p>I understand shell variables are local to the current shell while environment variables (the <code>export</code>ed ones) are passed onto child processes forked by the shell.</p>
  
  <p>When I run a Perl one-liner within double quotes I can access the (local) shell variable from the <code>fork</code>ed perl process:</p>
  
  <pre><code>$ FOO=bar
  $ perl -we "print qx'echo $FOO'"
  bar
  </code></pre>
  
  <p>Why is that?</p>