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Yes, Italy (or at least younger people in Italy) DOES celebrate Halloween. Maybe you'd like to edit this post, which was made with totally inappropriate certitude.
The Catholic church does not, of course, recognise Halloween, and in fact discourages its "celebration". It's primarily a US-originated festival, but has been growing in popularity throughout Europe over the past few decades. Read this for more info on Halloween in Italy:
http://www.lifeinitaly.com/culture/halloween.asp
I speak from personal experience here, as a lapsed Catholic with some knowledge of Halloween celebrations in continental Europe (and of course in the UK). It's rocketed in popularity recently - partly as an assimilation of American culture in general, and partly (in more Catholic countries such as Italy) as a minor rebellion against the established church.
The practice of dressing up in ghoulish costumes and going out partying ONLY applies to the relatively new (in Italy) festival of Halloween - i.e. the evening of the 31st October. Conversely, the traditional "Day of the Dead" - 2nd November - is marked only by visiting dead relatives' graves, and gathering together as a family for meals and gift giving. There is absolutely NO tradition of wearing ghoulish costumes on this day - in fact, to do so would be considered extremely disrespectful and almost immoral.
So, people should stop jumping to any sorts of conclusions that "Day of the Dead" in any way implies partying in costumes etc. It's a sober holiday that is still almost universally respected in Italy - even amongst the young. I guarantee that on the evening of November 2nd 2007, there would not have been groups of people wandering round Perugia dressed as witches, vampires or ghouls of any kind. And I can be almost as certain that people wouldn't be wearing such costumes on 1st November either.
To cut a long story short: The ONLY night on which people in Perugia would (or could) have been wearing ghoulish masks or costumes in any number would be October 31st.