how about the old fashioned way; when around a lot of people & the liar lies, tell everyone the truth that the person just lied, is a pathological liar, has been lying for years & he or she, needs to be correct right on the spot without hesitation!. liars can be highly conditioned to response from a developement in early childhood & never grow out of it. immediate correction is something that has traveled the "wind race" & got lost. remember the verse in which Jesus says tell the brother a correction, if he won't listen gather another & if he still won't listen, have nothing to do with him? & finally, pray for that person.
I agree that confrontation is the first thing on the list, but like the original post said, what if whenever they are caught out, they will lie their way out of that, unless the evidence is unavoidable and in those situations they always "humbly" admit that one thing, and agree with you, saying it is true they slipped up and have a weakness in that area but are doing their best and so on but this was a moment of weakness and they will do their best to ensure it doesn't happen again blah bah blah, and to all onlookers it is then you who seem to be unreasonable and unforgiving, when you know full well this is simply an act and the behaviour will continue until they are caught again in the future. Some people are very good at lying sadly, and any righteous anger or upset in the face of someone who is very good at acting contrite and humble, really goes against them.
Again I ask - What if you cant walk away from them and its your wife? or your husband? What if there isn't a reason for divorce, and you have to be with them, sleep with them and be intimate with them because scripture demands it?
What if its a parent and you are too young to pull away from their authority yet. You have to put up with it day in and day out, never being able to believe a word they say?
I think that is so so hard to imagine living with. And so so hard to counsel anyone in such a tricky situation if taking to them doesn't work, or if trying to out them back fires, and then just makes the situation worse at home. Yeah I still don't know what to advise someone in that situation and I do know for certain that there are people in just such a situation sadly. Whose daily life is one of gas-lighting, second guessing and never being able to take anything as real or true from someone so close to them.