Constatize a string without ActiveSupport (commonly come by default in rails) isn't friendly and in some case include AS is overkill. So, with this snipe you can constatize a String.
require 'net/http'
cls = "Net::HTTP".split('::').inject(Object) { |host,name| memo.const_get(name) }
# now you can use cls like normal constant
cls.new