context_probe.rb

# ====================
# Spell: Context Probe
# ====================

# Execute a block to access information in an object’s context.

class C
  def initialize
    @x = "a private instance variable"
  end
end

obj = C.new
obj.instance_eval { @x } # => "a private instance variable"

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