I will be thankful for any help.

Well, am not sure whether the following will be any help, but...

Looks like you're gathering and displaying IPs from a set of files, then printing 'Routing Loop Detected' at the end if an IP's been duplicated in that set.

An alternative to manually opening files is to use File::Slurp qw/read_file/;, as it returns a file's lines in a list context. Give this, and the excellent feedback already provided, consider the following option:

use Modern::Perl;
use File::Slurp qw/read_file/;
use Regexp::Common qw/net/;

sub R_loop2 {
    my ( $file, $loop, %seen ) = 'junk.txt';

    for my $fileName ( read_file $file ) {
        chomp $fileName;

        say 'The packet traversed this path:';
        for my $fileLine ( read_file $fileName ) {
            $fileLine =~ /($RE{net}{IPv4})/ or next;
            $loop++ if ++$seen{$1} > 1;
            say $1;
        }
    }

    if ($loop) {
        say 'Routing Loop Detected';
        return 1;
    }
}

[download]

Each line in the files whose names are contained in junk.txt is processed using Regexp::Common qw/net/ to match/capture IP addresses. Duplicate IPs are tracked, just before printing the IP address, by incrementing $loop, and 'Routing Loop Detected' will print at the end if $loop is set.

Hope this helps!

In reply to Re: No such file or directory at R_loop2.pl line 19. by Kenosis
in thread No such file or directory at R_loop2.pl line 19. by zakishah

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