This project needs a lot of doc work, but you can find the basic concept in the examples directory:
network_template.rbdefines a "resource group" which can be instantiated multiple times with different arguments. It's like a function, with some DSL sugar to establish a naming convention for related resources.vpc.rbuses the network template to create an actual network with three subnets.
Give it a try: bundle exec cfer generate examples/vpc.rb