How do you "inadvertently" state that you saw A, and then self-correct to "well, I didn't really see A like I just said I did?"
If you misremember the incident. It happens all the time.
For an example of intentional false swearing, we have Michael telling the police at the time of the incident that he and Terri had not been fighting. But they certainly had been fighting, with such ferocity that a worried friend offered to give Terri shelter that night for her safety. Michael lied to the cops. A reasonable person would call that perjury.