Depending on the number of IPs it might be slightly better performance if you used Regexp::Common and $RE{net}{IPv4} to extract out IP-address-looking-things from rule lines, then checked those against a hash for hits of interesting ones. Rather than running n different regular expressions over each firewall rule line n times, this runs one over only as many times as necessary to get out the IP-ish things in any given rule line and then you're doing a (much faster) hash existence test to see if that IP is a wanted one. 

use Regexp::Common qw( net );

my %interesting_ips;
while( <IPS> ) {
  chomp;
  $interesting_ips{ $_ } = 1;
}

while( my $fw_line = <RULES> ) {
  while( my( $addr ) = $fw_line =~ m{($RE{net}{IPv4})}g ) {
    say qq{$.: found interesting address '$addr'} 
      if exists $interesting_ips{ $addr };
  }
}

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The cake is a lie.
The cake is a lie.

In reply to Re: Sifting through firewall rules using a script by Fletch
in thread Sifting through firewall rules using a script by networkdude

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