Turning off echo in the Ruby console

Finally found the info, so keeping it here for the record:

In .irbc:

module IRB
  def self.echo_format
     conf[:PROMPT][conf[:PROMPT_MODE]][:RETURN]
  end

  def self.echo_format=(str)
     echo_format.replace(str)
  end

  def self.echo_on
     self.echo_format = "=> %s\n"
  end

  def self.echo_off
     self.echo_format = ''
  end
end 

Then in the console:

  >> IRB.echo_off