static L<WebRelation> webs_search_dollarXY_rel(final Web searchWeb, Collection<Web> webs) {
  new L<Map<WebNode>> mappings;
  for (Web web : webs)
    addIfNotNull(mappings, web_matchAllPerms_x(searchWeb, web, f nodeMatch_dollarVars));
    
  ret map(mappings, func(Map<WebNode> map) {
    map = web_addRelationsToMapping(map);
    ret web_getRelation(map.get(web_findNodeOrRelation(searchWeb, "$X")),
      map.get(web_findNodeOrRelation(searchWeb, "$Y")));
  });
}