Update: i Could break down the lengthy question to a simple:
How to overwrite a given line in a file with another line without appending?.

#!/usr/bin/perl
use strict;
use File::Copy;
use warnings;
my $open_file= "C:/oracle/ora81/network/ADMIN/SQLNET.ORA";
my $write_file=">>C:/oracle/ora81/network/ADMIN/SQLNET.ORA";
open(IN,$open_file) || die "cannot open $open_file $!";
open(OUT,$write_file) || die "cannot create $write_file $!";
while (<IN>) {
  if ($_ = /^SQLNET\.AUTHENTICATION_SERVICES=\ \(NTS\)$/){
    print  "\#\ ^SQLNET\.AUTHENTICATION_SERVICES=\ (NTS)";
    print OUT $_  "\#\ SQLNET\.AUTHENTICATION_SERVICES=\ (NTS)";
#Want to write the 2nd string print ... to OUT write handle  
#OUT $_
  }
}
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I want the print state in the while loop to write to the OUT Filehandle, i got a syntax error if i try this? Any Ideas where my error is? error message:

String found where operator expected at ora.pl line 22, near "$_  "\#\
+ SQLNET\.AUTHENTICATION_SERVICES=\ (NTS)""
    (Missing operator before "\#\ SQLNET\.AUTHENTICATION_SERVICES=\ (N
+TS)"?)
syntax error at ora.pl line 22, near "$_  "\#\ SQLNET\.AUTHENTICATION_
+SERVICES=\ (NTS)""
Execution of ora.pl aborted due to compilation errors.
[download]

Thanks
MH