What is required of one who has (inadvertently) said the salaam after two rak‘ahs of Dhuhr prayer?

If someone prays two rak'ahs, thinking they have completed their prayer, then remembers shortly thereafter, according to custom, that they have not, they must complete the remainder of their prayer, then say the taslim, then perform the prostrations of forgetfulness (sujud al-sahw), then say the taslim again. However, if a long interval passes, such as leaving the mosque or engaging in lengthy conversation unrelated to the prayer, they must repeat the entire prayer, as mentioned in the hadith of Dhul-Yadain.