This creates an artificial sort order, in order to implement higher priority for specifed elements (Up to 9999 of these).

#!/bin/perl -w
use strict;
use XML::Twig;

my $twig= XML::Twig->new(pretty_print=>'indented');

$twig->parse(\*DATA);
my $root=$twig->root;

$root->first_child->sort_children_on_att("type");

#Specify list of items (mainterm) that are forced FIRST in the sort or
+der
sort_my_kids($root,['mainterm',]);

$twig->print;

sub sort_my_kids{
   my ($me,$OrderTheseFirst) = @_;
   $me->sort_children(
         # Use special sort "get_key" sub, to specify artificial sort 
+order
         # Generated key is: 4-digit "Specified order", Tag, Value
     sub{my $el=shift; 
             my $tag=$el->tag; 
             my ($i)= (grep({$tag eq $OrderTheseFirst->[$_]} 0..$#$Ord
+erTheseFirst) , 9999);
             ##Debug# printf "  %04d%s\t",$i,$tag;
             return (sprintf "%04d%s%s",$i,$tag,$el->text_only());
             }        
    );
    foreach my $kid($me->children){
        sort_my_kids($kid,$OrderTheseFirst); # Recursive
    }    
}
[download]

Thank you Dear, your coding is fentastic. This solution is working. Even I did my code as below. But my code was specific to elements.Here is my code

#!/usr/bin/perl
use strict;
use warnings;
use XML::Twig;

my (@sortedM, @sortedL);
my $i=0;
my $twig= new XML::Twig(twig_handlers => { 
                                'enhancement' => sub {$_->first_child-
+>sort_children_on_att("type");},
                                'descriptor' => \&sortSubEltsHandler,
                            },
                        pretty_print => 'indented',    
            keep_atts_order => 1,
            );            
$twig->parse(\*DATA); 
$twig->print;
$twig->purge;

sub sortSubEltsHandler
{     
    my( $t,$elt)= @_;
    my $root= $t->root;    
    my @mainterms = $root->descendants(q{mainterm});
       @sortedM = reverse sort { $a->text cmp $b->text }
        @mainterms;
    my @links = $root->descendants(q{link});
       @sortedL =reverse sort { $a->text cmp $b->text }
        @links;
    $elt->cut_children;
    foreach my $mainterm (@sortedM) {
    my $new_elt= XML::Twig::Elt->new($mainterm->name => $mainterm->tex
+t);
    $new_elt->paste($elt);
    }
    foreach my $link (@sortedL) {
    my $new_elt= XML::Twig::Elt->new($link->name => $link->text);
    $new_elt->paste($elt);
    }
}#end of sortSubEltsHandler

__DATA__
<enhancement>
<descriptorgroup>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="a">plague</mainterm>
<mainterm>disease</mainterm>
<mainterm>pestilence</mainterm>
<link>f</link>
<link>C</link>
<link>M</link>
</descriptor>
</descriptors>
<descriptors type="DRG" controlled="y">
<descriptor>
<mainterm>panadol</mainterm>
<mainterm weight="a">zorro</mainterm>
<mainterm>xenon</mainterm>
<mainterm weight="a">aspirin</mainterm>
<link>b</link>
<link>P</link>
<link>z</link>
</descriptor>
</descriptors>
</descriptorgroup>
</enhancement>
[download]

hi NetWallah, I am getting below warning messages more than 200 times. When I ran earlier your code, I did not get this message. now I am getting this. I even added prints in between to check where the variable is not initialized. I could not trace. Use of uninitialized value in string comparison (cmp) at C:/Perl/site/lib/XML/twig.pm line 8820, <DATAFILE> line 9. XML I have tested is as below. Earlier xml was simple, but this is complex. Could u please help me how to solve this error. thank you in advance

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