According to 18 USC § 1621 – Perjury Generally

Whoever—
(1) having taken an oath before a competent tribunal, officer, or person, in any case in which a law of the United States authorizes an oath to be administered, that he will testify, declare, depose, or certify truly, or that any written testimony, declaration, deposition, or certificate by him subscribed, is true, willfully and contrary to such oath states or subscribes any material matter which he does not believe to be true; or
(2) in any declaration, certificate, verification, or statement under penalty of perjury as permitted under section 1746 of title 28, United States Code, willfully subscribes as true any material matter which he does not believe to be true; is guilty of perjury and shall, except as otherwise expressly provided by law, be fined under this title or imprisoned not more than five years, or both. This section is applicable whether the statement or subscription is made within or without the United States.

Perjury is a crime.

Law Info describes perjury this way:

While many people consider perjury and lying to be interchangeable terms, they are different. Perjury is a federal crime, and like all federal crimes, certain elements must be present in order for a person to be guilty of the crime. The federal crime of perjury is defined in the U.S. Code at 18 USC 1621. According to that law a person perjures himself if:
· He has taken an oath before a competent tribunal, officer, or person,
· In any case in which a law of the United States authorizes an oath to be administered,
· That he will testify, declare, depose, or certify truly, or that any written testimony, declaration, deposition, or certificate by him subscribed, is true, and
· He willfully and contrary to such oath states or subscribes any material matter which he does not believe to be true.
Therefore, all lying does not constitute perjury. A person must have taken a proper oath promising to be truthful and the untruth must be about a material fact. For example, if a person lies about the number of children he has to hide the fact that he has an illegitimate child and that fact is not pertinent to the car accident case in which he’s testifying then the fact is likely not considered material and a perjury charge is likely unjustified.

You must be convicted of perjury.  Evidence must be presented that you lied about a material fact under oath.

Keep this in mind as the Left is running around screaming like their hair is on fire how Kavanaugh committed perjury because he said that a Devil’s Triangle is a drinking game and not what Creepy Porn Lawyer Tweeted it means and how Senator Whitehouse’s wife likes it.

Really, this sort of insane distortion of the truth and hyperbole fits in with all the progressive newspeak definitions we’ve seen since 2016.

From the people who brought you:

Nazi/Fascist = someone who believes in free speech and equality under the law.
Russian Bot = Middle American Republican voter

Now we have:

Perjury = I don’t believe Republicans
Rape apologist = someone who believes in the presumption of innocence