global

For `%foo{ { foo: 1 }, bar: 2 }`, :old is "{ { foo: 1 }, bar: 2 }" and this method returns " { foo: 1 }, bar: 2 " for last argument.

def stripped_old
  return nil if old.nil?
  old.sub!(/\A{/, '').sub!(/}\z/m, '')
end