After further consideration, if you're wanting to print up to 500 lines total for each unique IP#, you should try a hash instead of the array. Take a look at this:

open (LOG, "$fw_logfile") or die and mail_error($!);
open (OUTFILE, "+>>$outfile") or die and mail_error($!);

my %newIPseen;

foreach my $i ( @newips ) {
    $newIPseen{$i} = 0;
}

while (<LOG>) {
    foreach $i ( keys( %newIPseen ) ){
        unless ( $newIPseen{$i} == 500 ) {
            print OUTFILE if (/\;drop;[^"]*$i/) && $newIPseen{$i}++;
        }
    }
}
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Now, if you load the hash %newIPseen in the first place instead of the array @newips, you can get rid of the first foreach loop.