Mine

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<route>
  <vars>
    <site>
      <pattern>([a-z0-9\-\_]+)</pattern>
      <default>www</default>
    </site>
    <document>
      <pattern>([a-z0-9\-\_]+)</pattern>
      <default>index</default>
    </document>
    <lang>
      <pattern>([a-z]{2})</pattern>
      <default>fr</default>
    </lang>
    <format>
      <pattern>([a-z]{2,6})</pattern>
      <default>xhtml</default>
    </format>
    <args>
      <pattern>(\/.+)</pattern>
      <default>/</default>
    </args>
  </vars>
  <inputUri>*?(%site%:)(%document%(.%lang%)(.%format%))(%args%)</inputUri>
</route>