gistfile1.rb

require 'rubygems'
require 'sinatra'

get '/' do
  haml :index
end

post '/' do
  params[:upload][:tempfile].read
end

use_in_file_templates!

__END__

@@index
%form{:method=>"post",:action=>"/",:enctype=>"multipart/form-data"}
  %input{:name=>"upload", :type=>"file"}
  %input{:type=>"submit"}