map_find.rb

module Enumerable
  def map_find(default=nil)
    return enum_for(:map_find, default) unless block_given?

    each do |e|
      mapped = yield e
      return mapped if mapped
    end

    default
  end
end

# Examples:

url = MAX_RETRIES.times.map_find { get_url }

n = 100.times.map_find {|x| x + 10 if x % 10 == 8 }