We do regularly allow perjury, as a matter of tradition and practice in the US. Almost every judicial search or seizure order issued is issued following law enforcement perjury (sometimes trivial, sometimes major). I have yet to see a search warrant application that does not contain falsehoods (each and every one sworn under penalty of perjury), and I only have experience with ones that have been signed and issued.
Not to mention there may be no mechanism to bring the perjurer to justice. For instance, I was served a search warrant on the basis a DOG accused me of wrongdoing. How do you accuse a dog of perjury? Not to mention it was an anonymous, unnamed dog and the person who allegedly listened to the dog was also unnamed on the warrant, so it was 3rd degree interspecies hearsay.
