roboticus: Thanks a lot! Based upon my understanding of your program above, I wrote this small one: 
#!/usr/bin/perl -w
open ($FH,'| sort -n') or die($!);
while(<ARGV>){
        print $FH $_;
}
close $FH;

[download]
Thanks again for "__DATA__" as well. There is one thing I would like mention: I used to write FH instead of $FH in open() as the file-handler. But both of them work. I did not know it. Please have a look at this: 
[demo@localhost Perl]$ cat bar.pl
#!/usr/bin/perl -w
open (FH,'| sort') or die($!);
$count=0;
while(<ARGV>){
    print FH $_;
    print $count++ . "\n";
}
close FH;

[demo@localhost Perl]$ bar.pl words 
0
1
2
3
4
A
ABC
a to z
Buy
Why

[download]
The line numbers are being printed out first and then the sorted list of the words. That means (this is what I understand now) that the data are being fed to the "sort" command which returns its result when all the input to it is fed.

In reply to Re^2: Filehandles and Input and Output Filters by devarishi
in thread Filehandles and Input and Output Filters by devarishi

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