[
          for $c in collection("captains")
          where exists(for $m in collection("movies")
                       where some $moviecaptain in let $captain := $m.captain
                                                   return typeswitch ($captain)
                                                          case array return $captain()
                                                          default return $captain
                             satisfies
                             $moviecaptain eq $c.name
                       return $m)
          return $c.name
        ]
      

Result (run with Zorba): [ "James T. Kirk", "Jean-Luc Picard" ]