What is Perjury? You'll Know it when you See It...usually in Malicious Abuse of Process cases...

Perjury is the intentional act of swearing a false oath or falsifying an affirmation to tell the truth, whether spoken or in writing, concerning matters material to an official proceeding.

Perjury - Wikipedia

https://en.wikipedia.org/wiki/Perjury

Take this into consideration 

regarding perjury

"I know it when I see it"

The phrase was used in 1964 by United States Supreme Court Justice Potter Stewartto describe his threshold test for obscenity in Jacobellis v. Ohio.^[1][2][3] In explaining why the material at issue in the case was not obscene under the Roth test, and therefore was protected speech that could not be censored, Stewart wrote:

I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.^[4]

https://en.wikipedia.org/wiki/I_know_it_when_I_see_it

18 U.S. Code § 1623 - False declarations before grand jury or court ...

https://www.law.cornell.edu/uscode/text/18/1623

Whoever under oath (or in any declaration, certificate, verification, or statement under penalty of perjuryas permitted under section 1746 of title 28, United States ... (c) An indictment or information for violation of this section alleging that, in any proceedings before or ancillary to any court or grand jury of the United States, the ...