(command.CommandList
  children: [
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name name:PS4)
          op: assign_op.Equal
          rhs: 
            {(SQ <'-(${BASH_SOURCE}:${LINENO}): ${FUNCNAME[0]} - [${SHLVL},${BASH_SUBSHELL}, $?]\n'>)}
          spids: [0]
        )
      ]
    )
    (C {<shopt>} {<-s>} {<extdebug>})
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name name:_Dbg_libdir)
          op: assign_op.Equal
          rhs: {($ Id.VSub_DollarName '$abs_top_srcdir')}
          spids: [12]
        )
      ]
    )
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name name:shunit_file)
          op: assign_op.Equal
          rhs: {(${ Id.VSub_Name abs_top_srcdir) <'test/unit/shunit2'>}
          spids: [15]
        )
      ]
    )
    (C {<set>} {<-->} {(SQ <-q>)})
  ]
)