From radioquintanaroo.com
48 hours before the day of elections, election day, and 12 hours the day after election day constitutes as "ley seca". So if elections are on the 17th, then starting from midnight on the 15th, all of the 16th, all of the 17th, and until noon on the 18th no alcohol will be sold. Selling alcohol results in a steep fine and extra police are out during this time.One tip to remember is that speaking Spanish will help you greatly. You'll be treated differently than if you speak English all the time, it'll help you assimilate, and you'll be able to communicate easier. If you're looking to learn Spanish, the two programmes I recommend are Synergy Spanish and Speak From Day 1.
Perhaps it's because voting is a requirement, not a right and people are afraid that Peruvians will be too drunk to vote properly, or easily persuaded to vote a certain way.
Another odd law is that the day before the election police aren't allowed to detain people or send them to prison, except for sex crimes. (El sábado 16 no se podrá detener o enviar a prisión a los ciudadanos habilitados para votar, salvo flagrancia.)