I'd suggest that you use the code tags to better format your code snippet.
Couple of suggestions:
1) Use the Windows task scheduler to create a call to the script on a periodic basis, rather than in an eternal loop. That way, if server load is causing a problem with the tail system call, at least the script will restart next time around.
2) Avoid the use of the system call completely - use the File::Tail module from CPAN with something like:

use File::Tail;
  $file=File::Tail->new(name=>$name, maxinterval=>10);
  while (defined($line=$file->read)) {
      if ($line =~ m/accept Rejected. Max connection reached/i) {
          print "found max connections\n";
      }
  }
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Note: this will create a permanent loop, removing the need for the first suggestion!