One program, multiple files

A close relative of require is load. The main difference is that if you do this

require "required.rb"
require "required.rb"

nothing happens the second time; whereas if you do this

load "required.rb"
load "required.rb"

Ruby reads in the file twice.

Links

Audit Logging in Ruby and Rails
Complementing exceptions - Introducing monads for error handling in ruby

Articles

How to Delegate Methods in Ruby
Keep Your Ruby App Secure with Bundler
An Introduction to Lambdas in Ruby