A person is guilty of perjury, a misdemeanor, if in any official proceeding he or she makes a false statement under oath or equivalent affirmation, or swears or affirms the truth of a statement previously made, when the statement is material and he or she does not believe it to be true.

(a) No person shall be guilty of an offense under this section if he or she retracted the falsification in the course of the proceeding in which it was made before it became manifest that the falsification was or would be exposed and before the falsification substantially affected the proceeding.

(b) No person shall be convicted of an offense under this section where proof of falsity rests solely upon contradiction by testimony of a single person other than the defendant.