Personally I tend to add the 's' to make things plural, it means I can just 'Read the words' to turn much of the quickly-reread code into English without needing to play about with learning to read the @ as plural.

I'd say this is also the reason why people tend to use plurals for database tables, despite the fact that it's a table and hence plural.. it's just more natural to write select firstname from users where lastname='Jones' than select firstname from user where lastname='Jones'.

This can kind of mess up when you index admittedly, $users[0] just seems subtly wrong to my brain, with the plural suggesting I'm dealing with more than one user at this time. Generally I tend to end up with things such as foreach my $user (@users) though, which I find perfectly readable.

Guess this is one of those personal taste things. Ultimately it doesn't matter providing you're consistant. These are the things of which coding style guidelines are made.