Either the answer is trivial:

use warnings;
use strict;

print "<xyz>\n";
print <DATA>;
print "</xyz>\n";

__DATA__
<abc>This is ....</abc>
<abc>sddfd....</abc>
[download]

or there is a bunch of information missing from your question.

When you supply the missing information (I'm pretty sure you're not looking for the trivial answer) you would do well to show what you have tried so far.

You may find either XML::Twig or XML::TreeBuilder of some help in generating a solution to your problem.

Apology for the message. I want to make the number of lines short considering server space. Let me explain it in detail.
I have the code like this


<author-group>
     <auth>
        </auth>
     <auth>
        </auth>
     <auth>
        </auth>
<aff>
</aff>
<aff>
</aff>
<corres id="cor1">
</corres>
</author-group>
[download]

I want to group all <auth> tags in a separate tag like



<author-group>
<XXX>
     <auth>
        </auth>
     <auth>
        </auth>
     <auth>
        </auth>
<XXX>
<aff>
</aff>
<aff>
</aff>
<corres id="cor1">
</corres>
</author-group>
[download]

I tried this using regular expression. I can’t get the “</auth>carriage return <aff>”. Please advice.

Could you please suggest any book to learn basics of perl.

Edit: g0n - code tags

Learning Perl would be a good book to start with. You may find that the monastery's Tutorials section is good for a quick start.

Here's a starting point for your XML manipulation using XML::TreeBuilder:

use strict;
use warnings;
use XML::TreeBuilder;

my $xml = <<XML;
<author-group>
<auth> </auth> <auth> </auth> <auth> </auth>
<aff> </aff> <aff> </aff>
<corres id="cor1"> </corres>
</author-group>
XML

my $root = XML::TreeBuilder->new ();

$root->parse ($xml);

for my $group ($root->look_down ('_tag', 'author-group')) {
    my @auths = $group->look_down ('_tag', 'auth');
    my $newRoot = HTML::Element->new ('xxx');
    
    $_->detach () for @auths;
    $newRoot->push_content (@auths);
    $group->unshift_content ($newRoot);
}

print $root->as_XML ();
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Prints:

<author-group><xxx><auth> </auth><auth> </auth><auth> </auth></xxx>
  
<aff> </aff> <aff> </aff>
<corres id="cor1"> </corres>
</author-group>
[download]

Still pretty trivial eh.;)

---

DWIM is Perl's answer to Gödel

As far as learning Perl basics goes, "Learning Perl", published by O'Reilly & Associates, is excellent. I bought it years ago, and I still refer to it.