Ruby: How to get API and manipulate it

With simply ruby no rails how can I call an API (ex: http://api.anapi.com/) and later manipulate it say to get a value from it and check if it is greater than 5.

http://api.anapi.com/: Say it contains an array called "anarray" which contains hashes: in one of those hashes I want to get to value of the key name "key".

How do I do this, again with only ruby.

Right now with this:

require "net/https"
require "uri"

uri = URI.parse("http://ift.tt/1GRr2lN")
http = Net::HTTP.new(uri.host, uri.port)

request = Net::HTTP::Get.new(uri.request_uri)

response = http.request(request)
puts response.body

I get: #<StringIO:0x2cadb90>

Thank you very much. Please let me know if I need to be clearer.