I'm learning modal verbs now and get in trouble with "need" one.
In my textbook it is said that:
don't need to == needn't -- present simple
didn't need to -- past simple
needn't have done -- present perfect
In some inexplicable reason I think that needn't have done sounds weird (may be because I haven't ever heard of such construction).
So my question is: Is there a sentence that equal to needn't have done but without the needn't part (like the past simple one)? Or everything is just fine with it and I shouldn't keep in mind?