regret doing vs regret having done

[Yun]

I know the difference in the meaning between “regret + gerund” and “regret + infinitive”

(A) regret + doing: feel sorry about what I did in the past.
(B) regret + to do: feel sorry about what I will do now.

However, I don’t exactly understand what difference exists in the below two sentences.
Could you please explain it to me?

(A) I regret not working harder.
(B) I regret not having worked harder.

[Bridget]

(A) can refer to the past or present, but (B) refers only to the past.

[Yun]

(A) can refer to the past or present, but (B) refers only to the past.

Thank you for reply.
For my easy understanding, would you take an example sentence in which "regret + doing" refers to the past?

[Marius Hancu]

Yes,

I regret not doing that yesterday AT 7PM. [at exactly that time
I regret not having done that yesterday BY 7PM. [before that time

are both correct, but the 2nd is used when actions are completed BEFORE a time limit. In both the regretting is at this time, in the present, the doing is in the past.

You see, both are non-finite forms, and the assignment of exact times are difficult without context. They can both work even in the future.

Also, the prepositions used are important.

[Yun]

Yes,

I regret not doing that yesterday AT 7PM. [at exactly that time
I regret not having done that yesterday BY 7PM. [before that time

are both correct, but the 2nd is used when actions are completed BEFORE a time limit.

You see, both are non-finite forms, and the assignment of exact times are difficult without context. They can both work even in the future.

Also, the prepositions used are important.

Thank you Marius.
But I intended to say referring to the present, not the past.

[Marius Hancu]

(A) I regret not working harder. [the regret is in the present; the working could be now or in the past

(B) I regret not having worked harder.[the regret is now, in the present; the working is in the past.

[Marius Hancu]

I edited both of my postings. Is everything clear now wrt to the times of the "regretting" and the "working/doing?"

[Yun]

I edited both of my postings. Is everything clear now wrt to the times of the "regretting" and the "working/doing?"

Thank you very much.
By the way, it seems that only you are actively helping learners.
I hardly see other advisors here.

[Marius Hancu]

Oh, there's OddThomas, Pete, Rusty, .... Perhaps they have less time right now. It varies.