while going through input file with each line as below format with below script

--file--
server1 M.22 s.23 2 AB 192.16.1.1 0 42 BBS 50
server3 M.22 s.33 2 AB 192.16.1.2 0 42 BBS 50 MK
server3 M.49 s.49 3 BB 10.1.1.1 0 42 BS 50
and more............
Program runs fine but I am only trying to replace 10th field's 50 with something else and since data is random, sometimes field 3 has 50 or 150 on it and messing up the program.
Can someone please give me a pointer for me to write this better ?
I am guessing 
 if ($cou) {
               $orig =~ s/\b$itemY\b/$default/;
               print "$orig\n";

[download]
is just looking at whichever 50 that occurs first and doing the substituion.
Can someone please give me a pointer on this

while (<>) {
   chomp;
   my $orig = $_;

   if ($orig =~ /^#/) {
        print "$_\n";
        next;
   }
   if ($orig =~ /^$/) {
        print "$_\n";
        next;
   }
   if (/(\w+)\s+M\.\d+\s+(s\.\d+)\s+(\S+\s+){6}(\d+)(.+)?$/) {
   #server1  yahoo.22  s.50   2   ABCCD     192.168.1.1    0   42  BBS
+  50
       my $cou = 1;
       my $item = join('@', $2, $1);
       my $itemY = $4;
       for my $i_carriers (keys %s_carriers) {
           if ("$item" eq "$i_carriers") {
               my $itemX = $s_carriers{$item};
               $orig =~ s/\b$itemY\b/$itemX/;
               print "$orig\n";
               $cou = 0;
           }
           last if ! $cou;
       }
       if ($cou) {
               $orig =~ s/\b$itemY\b/$default/;
               print "$orig\n";
       }
   }
}

[download]

In reply to regex question by convenientstore

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