[2021] MOVED: question about learn perks with items like the nerdy glasses

It is not lost permanently, but, you do lose access to the perk until such a time as your int reaches 8 again; be it via the glasses or via purchasing level 8 int properly.

This applies to ALL stat bonuses from items and foods- While active, you can purchase skills that require the raised stat; but when the temporary buff is removed, you lose access to the skill(s) till you get the requisite stat again.