My attempt at this metaprogramming balleyhoo. Did I really need to use eval?

attr_boolean.rb

#!/usr/bin/env ruby

require 'ripper'

class Module
  # Public: Defines a behooked getter for the given attribute names.
  #
  # symbols  - names of the @attribute to access. 
  #     
  def attr_boolean(*symbols)
    symbols.each do |symbol|

      # Ensure the symbol is exactly *one* identifier!
      ident, *rest = Ripper.lex(symbol.to_s)
      raise SyntaxError unless rest.empty?
      _, type, attr = ident
      # Only accept idenfiers as valid.
      raise SyntaxError unless type == :on_ident
      attr = attr.chomp '?'

      method = eval "Proc.new { @#{attr} }"
      define_method("#{attr}?", &method)
    end
  end
end