What you have is a pretty specific solution, and as such, is really only useful for you. But, you can indeed trim the code down. Here is one to do that:

use strict;
use warnings;
use XML::Simple;
use Data::Dumper;
 
my $data = XMLin(\*DATA, ForceArray => 1);
 
for my $trans (@{ $data->{trans} }) {
    next unless $trans->{kool} eq 'max';
    $trans->{item} = [$trans->{item}] unless ref $trans->{item} eq 'AR
+RAY';
 
    push @{ $trans->{item} }, {
        maxis => { assignee => ['jill'], status => ['con'] }
    };
}
 
print XMLout($data, KeyAttr => 'id');
 
__DATA__
<opt>
 <trans kool="max">
  <item id="legas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
 <trans kool ="kool">
  <item id="gas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
</opt>
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

Thanks Jeffa for your other way to trim the code down. I think, I have a problem because how do I know "trans" is the last one of my XML file.

For example I have in this XML file, the last "trans" is kool:

<opt>
 <trans kool="max">
  <item id="legas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
 <trans kool="sss">
  <item id="legas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
 <trans kool ="kool">
  <item id="gas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
</opt>
[download]


I think I need to use a loop with a counter. What do you think Jeffa?

Maxim

First, you hardly ever need an extra counter when you loop in Perl. That is a hold over from other languages, i had the same bad habit myself when i started Perl. Second, since you know which <trans> you want, the one with kool="kool", then you don't need to worry about counting them: just "ask" for the <trans> tag with attribute kool that is set to "kool". Third, use the right tool for the right job. In this case, XML::Twig is the Vorpal Blade you seek:

use strict;
use warnings;
use XML::Twig;
 
my $twig = XML::Twig->new(pretty_print => 'indented');
my $data = do {local $/;<DATA>};
$twig->parse($data);
 
my $root  = $twig->root;
my @trans = $root->children;
 
for my $trans (@trans) {
    next unless $trans->att('kool') eq 'kool';
 
    my $item = XML::Twig::Elt->new(item => { id => 'maxis'});
 
    my $assignee = XML::Twig::Elt->new(assignee => 'Jill')
        ->paste(last_child => $item);
 
    my $status = XML::Twig::Elt->new(status => 'con')
        ->paste(last_child => $item);
 
    $item->paste(last_child => $trans);
}
 
$twig->print;
 
__DATA__
<opt>
 <trans kool="max">
  <item id="legas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
 <trans kool ="kool">
  <item id="gas">
    <status>contacted</status>
    <assignee>jack</assignee>
  </item>
 </trans>
</opt>
[download]

See? No need for an extraneous counter, the next unless $trans->att('kool') eq 'kool'; line will skip all <trans> tags that do not have an attribute named kool set to "kool".

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

I'm intrigued by what you expect keyattr => 1 to do.

Setting KeyAttr to a scalar like this ...

... probably ought to throw an exception, but in fact it's an undocumented way to do this ...

... but setting it to '1' makes no sense at all since '1' is not a valid name for an XML attribute. Perhaps what you want to do is turn array folding off altogether, in which case you should set KeyAttr to an empty list: