You code did not duplicate the data. Propably you did not show the important part. However, you should use strict and use warnings;. Check open for errors and propably use binmode on your filehandles. Here is a cleaned version from your code. Untested... Ups, add the flocks. 
use strict;
use warnings;
use CGI qw/:standard/;
use Fcntl ':flock';

my ( @dataWrite, @dataRead );

open( my $in, "<", "../Rules1.txt" ) or die $!;
binmode $in;
flock($in, LOCK_SH);
@dataWrite = @dataRead = <$in>;
flock($in, LOCK_UN);
close $in;

push @dataWrite, "Code1\n";

open( my $out, ">", "../Rules1.txt" ) or dienice("Can't open counter.t
+xt: $!");
binmode $out;
flock($out,LOCK_EX);
print $out @dataWrite;
flock($out,LOCK_UN);
close $out;

print "Content-type: text/html\n";
print("\n");

[download]
Boris

In reply to Re: file duplication error by borisz
in thread file duplication error by Roy.Amitabh

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.