(command.ShAssignment
  pairs: [
    (assign_pair
      lhs: (sh_lhs_expr.Name name:workdir)
      op: assign_op.Equal
      rhs: 
        {
          (command_sub
            left_token: <Id.Left_DollarParen '$('>
            child: 
              (command.CommandList
                children: [
                  (command.Sentence
                    child: 
                      (command.ShAssignment
                        pairs: [
                          (assign_pair
                            lhs: (sh_lhs_expr.Name name:x)
                            op: assign_op.Equal
                            rhs: {<1>}
                            spids: [5]
                          )
                        ]
                      )
                    terminator: <Id.Op_Semi _>
                  )
                  (C {<pwd>})
                ]
              )
          )
        }
      spids: [3]
    )
  ]
)