title: How do you construct a read-write pipe with lua?
body: <p>I'd like to do the equivalent of:</p>
  
  <pre><code>foo=$(echo "$foo"|someprogram)
  </code></pre>
  
  <p>within lua -- ie, I've got a variable containing a bunch of text, and I'd like to run it through a filter (implemented in python as it happens).</p>
  
  <p>Any hints?</p>
  
  <p>Added: would really like to do this without using a temporary file</p>