~ㄹ/을 걸 그랬다 (~eul geol geu-reut-da) – I should have done (this/that instead)
When you want to express a regret that you should have done this/that instead of something else that you did, you can use ~ㄹ/을 걸 그랬다.
걸 (것을) = thing/object
그랬다 = like that (past tense)
You would typically attach a verb before ~ㄹ/을 걸 그랬다 because the main point here is to emphasise that you should have done this or that.
Example: 지금 비가 오네… 일찍 집에서 나갈 걸 그랬어…
Oh, it’s raining now… I should have went out of the house earlier…
시험을 잘 못 봤는데 예전에 더 열심히 공부할 걸 그랬지…
I didn’t do well for my test, I should have studied harder, shouldn’t I…
