This seems to be what happened:
Conservative party officials tried to bribe a dying independent MP to vote to bring down the Martin government. According to his widow, they offered him a million-dollar life insurance policy.
Harper discussed this issue with author Tom Zytaruk. Zyartuk taped the interview.
Later, Harper denied that he knew about the bribe and claimed the tape was doctored.
Harper got an injunction preventing the Liberals from using the tape and sued the Liberal party for libel for $3.5M. Harper won a delay in the trial until after next Tuesday's election.
Only the people in the room during the taping knew the truth about what Harper said. One of those people was Harper.
Now it has been revealed that the tape was not doctored.
Is there any explanation other than that Harper perjured himself?
(He apparently thought he was safe denying the tape because experts said that it was doctored. However, it turns out that while part of the conversation was recorded over, the damning part of the tape was clean.)