How to prove perjury?

When a person, under oath, lies about easily verifiable facts, such as their name, age, birth certificate, etc.,perjury is relatively simple to prove through the use of birth certificates, school records. a driver's license, State Identification Card and the like.

Now if the facts aren't easily verifiable, you will most likely need a witness or two, who are able provide verifiable, and irrefutable proof, that the person knowingly committed perjury, with the intent to deceive or cause some type of harm to another.