https://extragumpromo.com.au/form
I've now got 72 packs of Extra gum with this promotion on the front, from the official Extra store on amazon.com.au (NSW).
If you have an Aussie (maybe OzBargain) friend who's an enthusiast for prize comps, and would take say 10 unique codes from my Extra packs and make good use of them, let me know.
One entry per person per day, entries closing on the 26th.
They say to keep the receipt for proof of purchase, but any receipt for x2 packs of Extra gum (must be x2 or more in one transaction) from Woolworths etc. may suffice. Because it's just x5 $5000 e-vouchers at stake, I doubt they'll put the unique codes under the microscope.