class Hash

def deep_merge!(other, &block)
  other.each_pair do |key, val|
    tval = self[key]
    if tval.is_a?(Hash) && val.is_a?(Hash)
      self[key] = tval.deep_merge(val)
    else
      self[key] = block && tval ? block.call(k, tval, val) : val
    end
  end
  self
end unless method_defined? :deep_merge!