p:text-join 012 (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:text-join suffix="Injected text." override-content-type="text">
      <p:with-input>
         <p:inline content-type="text/plain">Text</p:inline>
      </p:with-input>
   </p:text-join>
   <p:identity>
      <p:with-input>
         <result>{p:document-property(., 'content-type')}</result>
      </p:with-input>
   </p:identity>
</p:declare-step>