A guy is standing on the corner of the street smoking one cigarette after another.

 A lady walking by notices him and says

"Hey, don't you know that those things can kill you? I mean, didn't you see the giant warning on the box?!"
"That's OK" says the guy, puffing casually "I'm a computer programmer"
"So? What's that got to do with anything?"
"We don't care about warnings. We only care about errors."