1.regret ding sth/that:对某事感到懊悔,遗憾
I regret that you see it like that.
I believe you will regret leaving Paris.
3.regret to do sth.that为要做的事抱歉,遗憾
I regret to say that I am unable
regret to have done将来完成时
regret having done:为做过的事感到后悔,抱歉