deep_transform.rb

# block gets key, value of each hash entry whose value is not a Hash or Array,
#       should return a new key and value for that entry.
def deep_transform(obj, &block)
  case obj
  when Hash
    obj.map do |key, val|
      case val
      when Hash, Array
        [key, deep_transform(val, &block)]
      else
        yield key, val
      end
    end.to_h
  when Array
    obj.map { |val| deep_transform(val, &block) }
  else
    obj
  end
end