false witness vs perjurer

false witness and perjurer both are nouns.

Word	Noun	Adjective	Verb	Adverb
false witness	Yes	No	No	No
perjurer	Yes	No	No	No

As nouns, false witness and perjurer are synonyms defined as:

false witness and perjurer: a person who deliberately gives false testimony

false witness (noun)	perjurer (noun)
a person who deliberately gives false testimony	a person who deliberately gives false testimony