The pipeline
<p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
<p:output port="result"/>
<p:identity>
<p:with-input>
<doc1/>
<doc2/>
</p:with-input>
</p:identity>
<p:for-each name="for-each">
<p:output port="result" primary="false">
<p:pipe step="identity" port="result"/>
</p:output>
<p:output port="secondary">
<p:pipe step="secondary" port="result"/>
</p:output>
<p:identity name="secondary">
<p:with-input>
<secondary/>
</p:with-input>
</p:identity>
<p:identity name="identity">
<p:with-input pipe="current@for-each"/>
</p:identity>
</p:for-each>
<p:wrap-sequence wrapper="result">
<p:with-input>
<p:pipe step="for-each" port="result"/>
<p:pipe step="for-each" port="secondary"/>
</p:with-input>
</p:wrap-sequence>
</p:declare-step>
Schematron validation
<s:schema xmlns="http://www.w3.org/1999/xhtml" xmlns:s="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
<s:pattern>
<s:rule context="/">
<s:assert test="result">The document root is not 'result'.</s:assert>
<s:assert test="result/*[1]/name()='doc1'">First child is not 'doc1'.</s:assert>
<s:assert test="result/*[2]/name()='doc2'">Second child is not 'doc2'.</s:assert>
<s:assert test="result/*[3]/name()='secondary'">Third child is not 'secondary'.</s:assert>
<s:assert test="result/*[4]/name()='secondary'">Fourth child is not 'secondary'.</s:assert>
</s:rule>
</s:pattern>
</s:schema>
