I think you want a single array-of-arrays variable rather than 12 individual variables, eg

push @{$stats[$month]}, $value;
...
for my $month (1..12) {
    print "NR ", scalar(@{$stats[$month]}), "\n";
    print $stats[$month][0], "\n";
}
[download]

update: As Corion reminded me, that should really be 0..11

Dave.