a Ruby implementation of the changes I explain in http://redmine.ruby-lang.org/issues/4539

zip.rb

# This is not efficient, it just shows the logic

class Array
  alias _zip zip
  def zip(*enums)
    if block_given?
      _zip(*enums).map(&Proc.new)
    elsif Symbol === enums.last
      sym = enums.pop
      _zip(*enums).map { |elements| elements.reduce(sym) }
    else
      _zip(*enums)
    end
  end
end

p [1,2,3].zip([6,5,4]) { |a,b| a+b } # => [7, 7, 7]
p [1,2,3].zip([6,5,4], :+) # => [7, 7, 7]