Indented puts Ruby Module, just include and go. You can also change the indentation size.

indentation.rb

class IndentedPutser
  attr_accessor :level

  def initialize(size)
    @level = 0
    @size = size
  end

  def indent
    self.level += 1
    yield self
    self.level -= 1
  end

  def puts(message)
    if !message.is_a?(String) && message.respond_to?(:to_s)
      message = message.to_s
    end
    Kernel.puts((' ' * @size * level) + message)
  end
end

module Indentation
  def indent(indentation_size = 3, &block)
    IndentedPutser.new(indentation_size).indent &block
  end
end

# example usage
indent do |i|
  i.puts 'level 1'
  i.indent do |i|
    i.puts 'level 2'
  end
end

The previous version messed up the binding to puts after being called