Problem 2 on Project Euler

p2.rb

class Numeric
  def even?
    self % 2 == 0
  end
end

module Enumerable
  def sum &blk
    blk = proc {|x| x} unless block_given?
    inject(0) {|sum, element| sum + (blk[element] || 0)}
  end
end

def fib(limit, *args)
  return [args.last] if args.sum > limit 
  fib(limit, args.last, args.sum) << args.first
end

puts fib(4000000, 1).sum {|n| n if n.even?}