No logic errors stand out immediately, but you're doing way too much work. For example,

$xf = 0;
    
$sthf->execute;
    
while (@dataf = $sthf->fetchrow_array())
{
    $filiais[$xf] = $dataf[0];
    $xf++;
}
[download]

is generally better written as:

while (my ($col) = $sthf->fetchrow_array())
{
    push @filiais, $col;
}
[download]

Similarly,

 for ($m=1; $m<=12; $m++)#Make an array of months
        {
            $months[$m] = $m;
        }
        
        foreach $months(@months)
        {
[download]

would be shorter, clearer, and prone to one less boundary condition as:

foreach my $month (1 ... 12)
{
[download]

The biggest issue you have is what appears to be a complete reliance on package globals. If you forget to reset one to zero at the start of the sub, you'll have values bleading over across invocations -- exactly what you describe. Change all of these variables into lexicals within your sub and I suspect your error will disappear.