"Might stop a hole to keep the wind away.
See in text (Act V - Scene I)
Notice that Hamlet picks up an AABB rhyme scheme in these lines, making these lines seem sing-songy and immature by comparison. He appears to be doing this to make fun of Horatio, who criticized him for thinking too much about death. By speaking in such melodic, rhyming couplets, he attempts to appear logical and precise even as he speaks with a kind of manic intensity.