Output port 31 (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"/>
   <p:try>
      <p:output port="result"/>
      <p:error code="error">
         <p:with-input>
            <error/>
         </p:with-input>
      </p:error>
      <p:catch code="error">
         <p:output port="result" content-types="text/plain"/>
         <p:identity>
            <p:with-input>
               <doc/>
            </p:with-input>
         </p:identity>
      </p:catch>
   </p:try>
</p:declare-step>