Output port 004 (AB)

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result" sequence="true"/>
   <p:group>
      <p:output port="result" sequence="false"/>
      <p:identity>
         <p:with-input>
            <doc/>
            <doc/>
         </p:with-input>
      </p:identity>
   </p:group>
</p:declare-step>