```ruby
class ENV_BANG
  module Classes
    class << self
      attr_writer :default_class

      def default_class
        @default_class ||= :StringUnlessFalsey
      end

      def cast(value, options = {})
        public_send(:"#{options.fetch(:class, default_class)}", value, options)
      end

      def boolean(value, options)
        !(value =~ /^(|0|disabled?|false|no|off)$/i)
      end

      def Array(value, options)
        options.delete(:class)
        options[:class] = options[:of] if options[:of]
        value.split(',').map { |value| cast(value.strip, options) }
      end

      def Symbol(value, options)
        value.to_sym
      end

      def StringUnlessFalsey(value, options)
        boolean(value, options) && value
      end

      # Delegate methods like Integer(), Float(), String(), etc. to the Kernel module
      def method_missing(klass, value, options, &block)
        Kernel.send(klass, value)
      end
    end
  end
end
```

Remove in-place modification of options when casting to Array.
user
```ruby
class ENV_BANG
  module Classes
    class << self
      attr_writer :default_class

      def default_class
        @default_class ||= :StringUnlessFalsey
      end

      def cast(value, options = {})
        public_send(:"#{options.fetch(:class, default_class)}", value, options)
      end

      def boolean(value, options)
        !(value =~ /^(|0|disabled?|false|no|off)$/i)
      end

      def Array(value, options)
        values = value.split(',').map { |value| value.strip }
        values.map! { |value| cast(value, class: options[:of]) } if options[:of]
        values
      end

      def Symbol(value, options)
        value.to_sym
      end

      def StringUnlessFalsey(value, options)
        boolean(value, options) && value
      end

      # Delegate methods like Integer(), Float(), String(), etc. to the Kernel module
      def method_missing(klass, value, options, &block)
        Kernel.send(klass, value)
      end
    end
  end
end
```
assistant