use strict;
use warnings;
#!/usr/bin/perl -w
use Regexp::Common qw/net/; 
open my $in, '<', 'Sample_01.txt' or die $!;
open FILE, '>', 'filename.txt' or die $!;

my %ipToRoute;
my $source_IP;
while (my $line = <$in>) {
      if (my ($ip) = $line =~ m/^Traceroute: .* (\S+)/) {	
		
        $source_IP = $ip;
    }
    else {
        $line =~ s/^ +//;
        my $destination_IP = (split / +/, $line)[1];
	push @{$ipToRoute{$source_IP}}, $destination_IP if $destination_IP ne '*';
	
    }
}

foreach my $source_IP (keys %ipToRoute) {
    my $final_destination = @{$ipToRoute{$source_IP}}[-1];
    if ($source_IP ne $final_destination) {
        print FILE "Destination to $source_IP but reached $final_destination\n";
    }
}