(   get$("[
    [[1, 2],
     [3, 4, 1],
     5]]",MEM,JSN)
  : ?template
&     (0.payload#0)
      (1.payload#1)
      (2.payload#2)
      (3.payload#3)
      (4.payload#4)
      (5.payload#5)
      (6.payload#6)
  : ?payloads
& ( instantiate
  =   tmplt plds pld a b
    .   !arg:(?tmplt.?plds)
      & (   !tmplt:#
          & !plds:? (!tmplt.?pld) ?
          & !pld
        |   !tmplt:%?a_%?b
          & (instantiate$(!a.!plds))_(instantiate$(!b.!plds))
        )
  )
& out$(jsn$(instantiate$(!template.!payloads)))
);