return.rb

module Enumerable
  def return(*)
    if block_given?
      each do |i|
        value = yield(i)
        return value if value
      end
      nil
    else
      super
    end
  end
end

h = {0 => 'a', 2 => 'b'}
[1,2,3].return {|x| h[x]} # => b
[4,5,6].return {|x| h[x]} # => nil