title: Displaying Error Message with Sinatra
body: <p>I'm writing a simple app that takes standard input from the user.  As for the email entry, I have it verify if it is in a standard email format and then have it list the problems like this when a new instance is going to be saved:</p>
  
  <pre><code>u = User.new
  u.email = params[:email]
  u.save
  if u.save
    redirect '/'
  else
    u.errors.each do |e|
      puts e
    end
  end
  </code></pre>
  
  <p>I know that if it is correct it should return back to the home page.  If it is wrong I want it to return to the home page as well, but I want it to return an error value (so I can have a pop-up or just something onscreen letting the user know that the format of the email was wrong).  What would be the best way to do this?</p>