Overpass-API/osm-3s_testing/input/rule_processor/rules.osm

<union>
  <query type="way">
    <has-kv k="triangle"/>
  </query>
  <query type="way">
    <has-kv k="shapes"/>
  </query>
</union>
<foreach into="way">
  <union>
    <recurse type="way-node" from="way"/>
    <item set="way"/>
  </union>
  <make-area pivot="way"/>
</foreach>

<query type="relation">
  <has-kv k="multpoly"/>
</query>
<foreach into="pivot">
  <union>
    <recurse type="relation-way" from="pivot"/>
    <recurse type="way-node"/>
  </union>
  <make-area pivot="pivot"/>
</foreach>