gistfile1.txt

require 'rubygems'
require 'sinatra'
require 'sinatra/captcha'
require 'erb'

get '/' do
  erb :captcha
end

post '/' do
  halt(401, "invalid captcha") unless captcha_pass?
  "passed!"
end

__END__

@@ captcha


and view/captcha.erb:
-------------------------

<%= captcha_image_tag %>

<%= captcha_answer_tag %>