(select
 (bgp
   (triple ?:x <http://example.org/ns#p> ?::?57)
   (triple ?::?57 |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:first ?:z)
   (triple ?::?57 |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:rest
           |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:nil))
 (?:x ?:z))