(command.CommandList
  children: [
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: 
                    (command.DBracket
                      expr: 
                        (bool_expr.Unary
                          op_id: Id.BoolUnary_f
                          child: {($ Id.VSub_DollarName '$_Dbg_libdir') <'/builtin/set0'>}
                        )
                    )
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (C {<enable>} {<-f>} {($ Id.VSub_DollarName '$_Dbg_libdir') <'/builtin/set0'>} {<set0>})
          ]
          spids: [61 74]
        )
      ]
    )
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: 
                    (command.Simple
                      words: [{<enable>} {<-a>} {<set0>}]
                      redirects: [
                        (redir
                          op: <Id.Redir_Great '2>'>
                          loc: (redir_loc.Fd fd:2)
                          arg: {<'/dev/null'>}
                        )
                      ]
                      do_fork: T
                    )
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (C {<_Dbg_help_add_sub>} {<set>} {<dollar0>} 
              {(SQ <'set dollar0 PROGRAM_NAME\n'> <'\n'> <'Set $0 to PROGRAM_NAME.'>)} {<1>}
            )
            (command.ShFunction
              name: _Dbg_do_set_dollar0
              body: 
                (BraceGroup
                  children: [
                    (command.If
                      arms: [
                        (if_arm
                          cond: 
                            (condition.Shell
                              commands: [
                                (command.Sentence
                                  child: 
                                    (command.Simple
                                      words: [{<enable>} {<-a>} {<set0>}]
                                      redirects: [
                                        (redir
                                          op: <Id.Redir_Great '2>'>
                                          loc: (redir_loc.Fd fd:2)
                                          arg: {<'/dev/null'>}
                                        )
                                      ]
                                      do_fork: T
                                    )
                                  terminator: <Id.Op_Semi _>
                                )
                              ]
                            )
                          action: [(C {<set0>} {(DQ ($ Id.VSub_Number '$1'))})]
                          spids: [142 155]
                        )
                      ]
                      else_action: [
                        (C {<_Dbg_errmsg>} {(DQ <'Can\'t do becasue set0 module is not loaded.'>)})
                      ]
                    )
                    (command.ControlFlow
                      token: <Id.ControlFlow_Return return>
                      arg_word: {<0>}
                    )
                  ]
                )
            )
          ]
          spids: [92 105]
        )
      ]
    )
  ]
)