There is a difference between the language מלבד הרעב הראשון (beside the first famine)⁷⁶⁰ and the language לבד מערי הפרזי (beside the unwalled towns)⁷⁶¹: Any place where it is possible to err and think that a matter is included in a statement, but it means to say that it is not included in the statement – it will say לבד מן. But in a place where it is impossible to err and think that a matter is included a statement and it only intends to inform that it is מלבד (in addition to), which says that it was more of a particular matter – it will say the word מלבד.

Genesis 26:1 says,ויהי רעב בארץ מלבד הרעב הראשון אשר היה בימי אברהם וילך יצחק אל אבימלך מלך פלשתים גררה(And there was a famine in the land, beside the first famine that was in the days of Abraham. And Isaac went to Abimelech king of the Philistines to Gerar), using the word מלבד (beside) to inform that the famine in the land in the days of Isaac was in addition to the first famine that was in the days of Abraham.

Deuteronomy 3:5 says,כל אלה ערים בצרות חומה גבהה דלתים ובריח לבד מערי הפרזי הרבה מאד(All these were fortified cities, with high walls, gates, and bars; beside the unwalled towns a great many), using the word לבד (beside) to say that one should not err and think the Torah is including the unwalled towns⁷⁶².

footnotes: ⁷⁶⁰ Genesis 26:1. ⁷⁶¹ Deuteronomy 3:5. ⁷⁶² Malbim, HaTorah v’HaMitzvah Emor 190.