about readdir call

Hello everyone,
 
I'm reading one directory using readdir call. but I'm getting different
output from that I got by 
running ls -l command on same directory manually. Following is the snippet
I'm using:
 
#!/usr/bin/perl -w
$dirname = "/test_dir";
opendir ( DIR, $dirname ) || die "Error in opening dir $dirname\n";
while( ($filename = readdir(DIR))){
     print("$filename\n");
}
closedir(DIR);
 
From above snippet I got following output:
.
..
2.OUTPUT
4.OUTPUT
1.OUTPUT
3.OUTPUT
5.OUTPUT

test_dir contains :
test_dir# ls -l
-rw-r--r-- 1 root root 72400 Jun  5 22:35 1.OUTPUT
-rw-r--r-- 1 root root 69785 Jun  5 22:33 2.OUTPUT
-rw-r--r-- 1 root root 69960 Jun  5 22:33 3.OUTPUT
-rw-r--r-- 1 root root 69785 Jun  5 22:33 4.OUTPUT
-rw-r--r-- 1 root root 69785 Jun  5 22:33 5.OUTPUT
This is what I was expecting from readdir call.
 
Order of files got disturbed.
 
Do anyone know reason why I'm getting such output? 
What are the modifications if I want output same to that of 'ls -l'?
Thanks in advance.
 
 
 
 
~~~~~~~~~~~~~~~~~~~~
Thanks and Best regards,
~ Rajnikant
Software Engg.
Persistent Sys. Ltd.
Ph. +91 98222 04088
 

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