I'm not sure of the technical names for the offences, but it's along the lines of driving in an unfit state, and if you're pulled you over for doing something really stupid or after a crash, you can be done for reckless endangerment of lives or culpable driving (someone who knows please help me out here with the actual terms). Depending on how lucky/unlucky you are, you can be done for pretty serious offences carrying quite stiff penalties...
As for trying to hide it - don't. If you have something to hide, you shouldn't be driving. I'm not sure if the actual pupil thing happens in Australia, but the test will be more to see if you can stand on one leg, or estimate time or something. Which if you're still fucked cannot be faked.
Plus, if you're in a decent accident there's every chance you'll be blood tested - and then you're really screwed...