bot.rb

class Array
  def shuffle!
    size.downto(1) { |n| push delete_at(rand(n)) }
    self
  end
end

require 'rubygems'
require 'twibot'

configure do |conf|
  conf.login = "botname"
  conf.password = "twitterpassword"
end

messages=[
            "Hi!",
            "Leave me alone!",
            "How are you?",
          ]

message do |message, params|
  post_tweet "@#{message.sender.screen_name} " + messages.shuffle![0] unless message.sender.screen_name == "botname"
end

reply do |message, params|
  post_tweet "@#{message.user.screen_name} " + messages.shuffle![0] unless message.user.screen_name == "botname"
end

execute.sh

ruby bot.rb

requires.sh

gem sources -a http://gems.github.com
sudo gem install twibot
sudo gem install twitter4r