From the blog post "Error Handling with Either Monads in Ruby"

do_notation.rb

def call(fields)
  fields = yield validate_fields(fields)
  email = yield validate_email(fields['email'])
  user = yield find_user(fields['id'])
  user = yield update_user(user, {name: fields['name'], email: fields['email']})
  sent = yield send_email(user, :profile_updated)

  Success(user)
end