Check the Spanish-language pages as well, because sometimes the Spanish pages are updated but the English ones not.
Also, something I learned recently, if you want to declare something you're taking out of the country and wish to return with without it counting towards your allowance, then you need to do a declaration before passing all the security checks in the airport.
I was taking a laptop out and wanted to bring back two laptops. Unfortunately I missed the desk where you do the declaration, and so I had no paperwork. The guy on the X-ray machine spotted my two laptops and I was just getting ready to plead my case when he obviously had pity or something and just let me go.
Also, various times my wife has had me bring in large numbers of pairs of trainers or branded clothes or whatever, and it seems that they are genuinely not interested in these. Once I tried to declare them and pay the tax, but I was told that I didn't need to put them on the list. However, 20 XBoxes, or two suitcases full of French cosmetics (genuine case I heard of) do set their SUNAT antennae twirling, so expect trouble in those cases.