Welcome to the monastery, the preview page explains how to mark up text so that it is formatted correctly, you should use <code> tags around your code like this, I have added a few, hopefully helpful, comments

use strict;   # these two lines will save you
use warnings; # endless head scratching

open(DAT, "text.txt"); # you open this file again in two lines
$data_file="<text.txt "; # three argument version of open is preferabl
+e
open(DAT, $data_file); # you should check the return value of open
@raw_data=<DAT>; #  Assumed this was what the line said
close(DAT);
foreach $student (@raw_data)
{
chomp($student);
($name,$roll_no,$class)=split(/\|/,$student);
print "The student $name bearing roll number $roll_no is in class $cla
+ss";
print "
\n";
}
[download]