Josh Marshall:

It's true that perjury charges can in some cases amount to 'gotchas', prosecutions brought for minor misstatements or possible lapses of memory.

This ain't one of those cases.

[...]

Far more important, however, is the rest of the information included in the indictment. If you read the recitation of events which takes up, roughly, the first half of the indictment, one thing is made very clear: Libby was in communication about what he was doing with all sorts of people at the White House while he was doing it.