wtf happen with variable

#=================================================
# ** Game_Interpreter
#------------------------------------------------------------------------------
#  An interpreter for executing event commands. This class is used within the
# Game_Map, Game_Troop, and Game_Event classes.
#======================================================

class Game_Interpreter
  #--------------------------------------------------------------------------
  # * Control Variables
  #--------------------------------------------------------------------------
  def command_122
    value = 0
    case @params[3]  # Operand
    when 0  # Constant
      value = @params[4]
    when 1  # Variable
      value = $game_variables[@params[4]]
    when 2  # Random
      value = @params[4] + rand(@params[5] - @params[4] + 1)
    when 3  # Item
      value = $game_party.item_number($data_items[@params[4]])
    when 4  # Actor
      actor = $game_actors[@params[4]]
      if actor != nil
        case @params[5]
        when 0  # Level
          value = actor.level
        when 1  # Experience
          value = actor.exp
        when 2  # HP
          value = actor.hp
        when 3  # MP
          value = actor.mp
        when 4  # Maximum HP
          value = actor.maxhp
        when 5  # Maximum MP
          value = actor.maxmp
        when 6  # Attack
          value = actor.atk
        when 7  # Defense
          value = actor.def
        when 8  # Spirit
          value = actor.spi
        when 9  # Agility
          value = actor.agi
        end
      end
    when 5  # Enemy
      enemy = $game_troop.members[@params[4]]
      if enemy != nil
        case @params[5]
        when 0  # HP
          value = enemy.hp
        when 1  # MP
          value = enemy.mp
        when 2  # Maximum HP
          value = enemy.maxhp
        when 3  # Maximum MP
          value = enemy.maxmp
        when 4  # Attack
          value = enemy.atk
        when 5  # Defense
          value = enemy.def
        when 6  # Spirit
          value = enemy.spi
        when 7  # Agility
          value = enemy.agi
        end
      end
    when 6  # Character
      character = get_character(@params[4])
      if character != nil
        case @params[5]
        when 0  # x-coordinate
          value = character.x
        when 1  # y-coordinate
          value = character.y
        when 2  # direction
          value = character.direction
        when 3  # screen x-coordinate
          value = character.screen_x
        when 4  # screen y-coordinate
          value = character.screen_y
        end
      end
    when 7  # Other
      case @params[4]
      when 0  # map ID
        value = $game_map.map_id
      when 1  # number of party members
        value = $game_party.members.size
      when 2  # gold
        value = $game_party.gold
      when 3  # steps
        value = $game_party.steps
      when 4  # play time
        value = Graphics.frame_count / Graphics.frame_rate
      when 5  # timer
        value = $game_system.timer / Graphics.frame_rate
      when 6  # save count
        value = $game_system.save_count
      end
    end
    for i in @params[0] .. @params[1]  # Batch control
      case @params[2]  # Operation
      when 0  # Set
        $game_variables[i] = value
      when 1  # Add
        $game_variables[i] += value
      when 2  # Sub
        $game_variables[i] -= value
      when 3  # Mul
        $game_variables[i] *= value
      when 4  # Div
        $game_variables[i] /= value if value != 0
      when 5  # Mod
        $game_variables[i] %= value if value != 0
      end
      if $game_variables[i] > 99999999    # Maximum limit check
        $game_variables[i] = 99999999
      end
      if $game_variables[i] < -99999999  # Minimum limit check
        $game_variables[i] = -99999999
      end
    end
    $game_map.need_refresh = true
    return true
  end
end