Honestly, this is so not the way you want to do an infinite list. I won't even get into the why (other responders already have), and Google can tell you the details of it better than I can anyway (although maybe not perl-specific, but the theory at least).

The following is the more commonly accepted way to go about such a thing.

my $counter = 0;
my $generator = sub { ++$counter };

while (1) {
    print $generator->();
}
[download]

To re-do your example it would be this:

my $gimme_an_A = sub { 'a' };

while (1) {
    print $gimme_an_A->();
}
[download]

Your approach is very memory wasteful since you have an infinitely growing @array, which will eventually consume all available system memory. The above versions never store previous values (which I can only assume you are never using anyway) so they can run in a pretty small and compact memory space.