When you need two (or more) concurrent loops like this, you can use threads. However, in this case you can just combine them into a single loop, as follows (untested):

my $time_slept = 0;

while (1)
{
    ...

    $time_slept += sleep $config{Database}->{Sleep};

    if ($time_slept >= 7200)
    {
        DB_Backup();
        $time_slept = 0;
    }
}
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Hope that helps,