Not true, but I'll play along ...
The question is if he lied about what he TOLD them.
Did he give false testimony if he says "I did know Plame's status with the CIA on July 1, 2003."?
-CORRECTION-
Make that "did NOT know of Plame on July 1, 2003." (except what I heard from reporters)
See? Confusing isn't it.
The Big Mo is not in the prosecutor's favor, and the defense hasn't even started. It is likely that other reporters will suddenly remember knowing about Plame, and it is likely their source will be the CIA itself, as with Woodward.
It's a good thing you're not going to be on the jury when Libby is tried.