$ ruby -v
If you're using Ruby 1.8.7, you'll have to modify the program. The problem is the main application source file
app.rb. Here's the program as AppFog provides it:
require 'sinatra' set :protection, except: :ip_spoofing get '/' do erb :index end
In Ruby 1.8.7, you have to explicitly indicate that you're using Gems. This is not necessary in later versions.
The set line is a workaround for a bug in the AppFog software. This bug has long since been fixed, but the set command does no harm in later versions of Ruby. However, it is syntactically incorrect in Ruby 1.8.7 so you should remove that line.
Edit the source code so it looks like this:
require 'rubygems' require 'sinatra' get '/' do erb :index end