You're right I should have stated CGI.
So I added:

my $q = new CGI;
my $userIP = $q->remote_addr();
[download]

And it works. Is there a way to mark a question closed?

Hello bartender1382 and welcome to the monastery and to the wonderful world of perl!

> .. I should have stated CGI

..and many of us could have answered: we wait for you in XXI century :)

No seriously and without any offending intent, you can glance CGI to understand some basic concepts but then (or from the beginning) look at something contemporary like Dancer2 or Mojolicious

L*

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

"Is there a way to mark a question closed?"

There's no need to do that. In fact, doing so may result in other, relevant information not being posted. Just leave the thread as is: you'll get a notification is someone else replies to you.

— Ken

This might be fun for you to add to those two lines:

use Net::Whois::IP ('whoisip_query');  # This module is not installed 
+automatically with a
                                        # Perl installation, so you'll
+ need to install it 
                                        # from CPAN in order to be abl
+e to use its 
                                        # whois_ip_query function.

use Fcntl (':flock');

if ($userIP) {

    my $location_of_some_log_file = '/var/logs/my_log_file.log';

    open ( my $log_fh, '>> :encoding(UTF-8)', $location_of_some_log_fi
+le )
      or die "FATAL: Trouble opening '$location_of_some_log_file' for 
+appending: $!";

    flock ( $log_fh, LOCK_EX );

    my $ip_whois_response = whoisip_query($userIP);
    if ($ip_whois_response) {
        print {$log_fh} "Running whois on IP address '", $userIP, "':\
+n\n";

        foreach ( sort keys( %{$ip_whois_response} ) ) {
            print {$log_fh} "$_ $ip_whois_response->{$_} \n";
        }
    }
    else {
        print {$log_fh} qq|Cannot run whois to do an IP lookup, becaus
+e no response received when invoking whoisip_query method of Perl mod
+ule Net::Whois::IP on IP '$userIP'\n\n|;
    }

    close $log_fh or warn "WARNING: Some trouble closing file handle f
+or '$location_of_some_log_file': $!";
}
[download]

EDITED 4/12/2022 -- corrected "use Net::Whois::IP ('whois_ip_query');" to read "use Net::Whois::IP ('whoisip_query');"