Knuth's code has bugs. NASA's code has bugs. I don't think our species has produced even one nontrivial correct program, much less a programmer who's competent (which I take to mean a large portion of their work is 100% correct). Our profession is passing through the mercury-and-leeches phase medicine once went through. Someday our descendants will look back from their error monad formal proofs or something and cringe at everything we did.