Same rule applies. Scarcely and barely are also negative in meaning, so they pair with can , not can’t .

✅ Hardly had I sat down when the phone rang. (Not: Hardly I had sat down... )

Logically, two negatives cancel each other out. If you say, "I can’t hardly wait," you are technically saying you cannot wait hardly (not much), which implies you can wait quite a lot. While listeners usually understand your intent, the phrasing is redundant and technically flips the meaning of the sentence. The Correct Form: "Can Hardly"

The correct phrasing is