scope_gate.rb

# =================
# Spell: Scope Gate
# =================

# Isolate a scope with the class, module, or def keyword.

a = 1
defined? a # => "local-variable"

module MyModule
  b = 1
  defined? a # => nil
  defined? b # => "local-variable"
end

defined? a # => "local-variable"
defined? b # => nil

# For more information: http://www.pragprog.com/titles/ppmetr/metaprogramming-ruby