Are you sure this is your code? $in_file2 isn't defined anywhere. Add use strict; use warnings;, fix the warnings given. Do you really have an and open(OUT, ">>port.txt"); for my $host = ....? You may also want to be careful with the scope of $ip, e.g.

my $ip = 1;
my @ip = qw (2 3 4);

foreach my $ip (@ip){
  print "$ip\n";
}
 
print "$ip\n";
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Update: fixed code tag typo, thanks Eily.