title: Use regex query with mongoexport
body: <p>I'm trying to export user datas filtered by case insensitive query :</p>
  <pre><code>mongoexport --quiet --assertExists --jsonArray --pretty --collection='users' --query='{&quot;email&quot;: {$regex: /^john.doe@gmail.com$/i}}' --uri='mongodb://dbhost:27017/mydatabase'
  </code></pre>
  <p>But this command returns nothing.</p>
  <p>If I use the same query in mongo shell, it works !</p>
  <pre><code>db.users.find({&quot;email&quot;: {$regex: /^john.doe@gmail.com$/i}})
  </code></pre>
  <p>I can't explain why. Is anybody can help me ?</p>