twitter_username_and_url_markup.rb

  def add_url_markup(text)
    urls = []
    users =[]
    # find urls
    text.split.each{|a| a=~/(http\:\/\/\S+)/; urls << $1}
    # find twitter usernames (@someusername)
    text.split.each{|a| a=~/(\@\S+)/; users << $1}
    # add markup
    users.compact.each{|user| text.gsub!(user, "<a href='http://twitter.com/#{user.gsub('@','')}'>#{user}</a>")}
    urls.compact.each{|url| text.gsub!(url, "<a href='#{url}'>#{url}</a>")}
    text
  end