(select
 (bgp
   (triple ?::?48 <http://example.org/ns#p> ?::?51)
   (triple ?::?51 |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:first ?::?49)
   (triple ?::?51 |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:rest ?::?50)
   (triple ?::?49 ?::pa ?:b)
   (triple ?::?50 |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:first 57)
   (triple ?::?50 |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:rest
           |http://www.w3.org/1999/02/22-rdf-syntax-ns#|:nil))
 (?:x ?:y ?::pa ?:b))