Hi,

I understand that gurus have responded you. Nevertheless, I'd like to add my 5 cents. What I've seen as a solution after I completed to read the thread.

1. grep input for any lines matching IP pattern
2. IPs after (1) should be tested for matching the IP list from the specified subnet

Before posting my answer I created tiny toy proving correctness of my approach:

#!/usr/bin/perl

use strict;
use warnings;

use Net::Subnet;

my $matcher = subnet_matcher qw(192.168.1.0/22);

while ( <DATA> ) {
    my @ips = m/(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25
+[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/g;
    next unless @ips;
    next unless grep { $matcher->($_) } @ips;
    print;
}

__DATA__
 
Sample output that I want to achieve: 

2017-12-08 07:01:39 127.0.0.1 GET /course-detail.aspx id=66&catColor=0
+ 443 - 127.0.0.1 (e.g., IP) <server version etc. strings> 200 0 0 530
2017-12-08 07:01:39 127.0.0.1 GET /course-detail.aspx id=66&catColor=0
+ 443 - 192.168.1.2 (e.g., IP) <server version etc. strings> 200 0 0 5
+30
2017-12-08 07:01:39 127.0.0.1 GET /course-detail.aspx id=66&catColor=0
+ 443 - 192.168.2.1 (e.g., IP) <server version etc. strings> 200 0 0 5
+30
2017-12-08 07:01:39 127.0.0.1 GET /course-detail.aspx id=66&catColor=0
+ 443 - 192.168.1.3 (e.g., IP) <server version etc. strings> 200 0 0 5
+30
2017-12-08 07:01:39 127.0.0.1 GET /course-detail.aspx id=66&catColor=0
+ 443 - 192.168.4.3 (e.g., IP) <server version etc. strings> 200 0 0 5
+30

#Note that I only want to grep IP addresses (192.168.1.1-3) that are i
+n the same netmask specified in $matcher
[download]

Please pay attention that netmask /22 corresponds to wide range of IPs 192.168.1.0 - 192.168.3.255.