Problem 6 on Project Euler

p6.rb

class Numeric
  def squared
    self * self
  end
end

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

puts (1..100).sum.squared - (1..100).sum {|i| i.squared}