I found this out the hard way
the permissions on the data file need to be set at least to 766 to allow writing and reading

here is a sample code that I was working on simular...

#!/usr/bin/perl

use CGI;
$data = new CGI;
$email = $data->param('email');


$datafile ="/full_path/data2.txt";

open (FORUM, "<$datafile");
@lines = <FORUM>;
close (FORUM);

$email="eww";
open (FORUM, ">$datafile");
print FORUM ("EMAIL");


print "Content-type: text/html\n\n";
print "$email";
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Hacker_J99
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