Please, format your post question effectively
Even when that is done. There are other some other best practice I think you should still look into.

• Avoid barewords usage like FILE, FH, etc. Instead use a lexically scoped variable like $fh etc
• use use warnings; use strict;
• use the 3 argument open function like so:open my $fh, '<',"config.txt" or die "cannot open file : $!";
• Close your file handles like so: close $fh or die "can't close file: $!";
• Your construction here will only print "1", after you have corrected the syntax error
  Use this instead:
  

  ...
  while(<$fh>){
  
    chomp;
      (my $ip =
         $_) =~ m/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/; 
    print $ip,$/;
  }
  ...
  [download]

  
  I think is even alot better to TEST each of your matched value using "if" like so:

  ...
  while (<$fh>) {
    chomp;
      my $ip="";
      if (m/(?<matched_ip>(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}))/){
        $ip = $+{matched_ip};
      } 
    print $ip,$/;
  }
  ...
  [download]