arc:exists

<arc:call op="fileListDir" output="out">
  <arc:exists attr="filename">
    <arc:set attr="title" value="[filename]"/>
    <arc:else>
      <arc:set attr="title" value="Unnamed File"/>
    </arc:else>
  </arc:exists>
  <arc:push title="[title]">
  [out.file:*] 
  </arc:push>
</arc:call>