count_hash.rb

class CountHash < Hash
  def initialize
    super(0)
  end

  def count(key)
    self[key] += 1
    self
  end
end

p 'these are some words and these are some more words'.split.reduce(CountHash.new, :count)
# => {"these"=>2, "are"=>2, "some"=>2, "words"=>2, "and"=>1, "more"=>1}