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

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

#$twig->parsefile("OpsbankII-im1.xml"); 
$twig->parse(\*DATA);
my $root=$twig->root;

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

$twig->print;
#----------
sub sort_my_kids{
    my $me = shift;
    $me->sort_children_on_value;
    foreach my $kid($me->children){
        sort_my_kids($kid); # Recursive
    }    
}  

__DATA__
<root>
<enhancement>
<descriptorgroup>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
algorithm
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
colon diverticulosis
</mainterm>
<link>
surgery
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
disease severity
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
human
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
recurrent disease
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
review
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
sigmoidectomy
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
surgical technique
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
treatment indication
</mainterm>
</descriptor>
</descriptors>
</descriptorgroup>
<classificationgroup>
<classifications type="ASJC">
<classification>
<classification-code>
2715
</classification-code>
</classification>
<classification>
<classification-code>
2746
</classification-code>
</classification>
</classifications>
</classificationgroup>
</enhancement>
<enhancement>
<descriptorgroup>
<descriptors type="DRG" controlled="y">
<descriptor>
<mainterm weight="a" candidate="n">
DNA binding protein
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
DNA polymerase
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
initiation factor
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
plasmid DNA
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
</descriptors>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
animal cell
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
article
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
chromatin
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
DNA replication
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
DNA replication origin
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
DNA supercoiling
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
egg
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
nonhuman
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
plasmid
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
Xenopus laevis
</mainterm>
</descriptor>
</descriptors>
<descriptors type="SPC" controlled="y">
<descriptor>
<mainterm candidate="n">
Animalia
</mainterm>
</descriptor>
<descriptor>
<mainterm candidate="n">
Eukaryota
</mainterm>
</descriptor>
<descriptor>
<mainterm candidate="n">
Xenopus laevis
</mainterm>
</descriptor>
</descriptors>
</descriptorgroup>
<classificationgroup>
<classifications type="ASJC">
<classification>
<classification-code>
1312
</classification-code>
</classification>
</classifications>
</classificationgroup>
<chemicalgroup>
<chemicals source="esbd">
<chemical>
<chemical-name>
37217-33-7
</chemical-name>
<cas-registry-number>
DNA polymerase
</cas-registry-number>
</chemical>
</chemicals>
</chemicalgroup>
</enhancement>
<enhancement>
<descriptorgroup>
<descriptors type="DRG" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
acetonitrile derivative
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
benzene derivative
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
cyclohexane derivative
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
lactic acid derivative
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
lactone derivative
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
organic solvent
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
poly(3 hydroxybutyric acid)
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="y">
poly(3 hydroxybutyric acid) depolymerase
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
polyhydroxyalkanoic acid
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
unclassified drug
</mainterm>
</descriptor>
</descriptors>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
article
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
catalysis
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
enzyme activity
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
esterification
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
hydrolysis
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
nonhuman
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
polymerization
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
Pseudomonas
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="y">
pseudomonas lemoignei
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
reaction analysis
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
stereochemistry
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
synthesis
</mainterm>
</descriptor>
</descriptors>
</descriptorgroup>
<classificationgroup>
<classifications type="ASJC">
<classification>
<classification-code>
1605
</classification-code>
</classification>
</classifications>
</classificationgroup>
<chemicalgroup>
<chemicals source="esbd">
<chemical>
<chemical-name>
26063-00-3
</chemical-name>
<cas-registry-number>
poly(3 hydroxybutyric acid)
</cas-registry-number>
</chemical>
</chemicals>
</chemicalgroup>
</enhancement>
<enhancement>
<descriptorgroup>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
axillary lymph node
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
breast carcinoma
</mainterm>
<link>
diagnosis
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
cancer staging
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
cancer surgery
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
human
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
lymph node dissection
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
lymph node metastasis
</mainterm>
<link>
complication
</link>
<link>
surgery
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
priority journal
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
prognosis
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
review
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
treatment outcome
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
treatment planning
</mainterm>
</descriptor>
</descriptors>
</descriptorgroup>
<classificationgroup>
<classifications type="ASJC">
<classification>
<classification-code>
1306
</classification-code>
</classification>
<classification>
<classification-code>
2730
</classification-code>
</classification>
</classifications>
</classificationgroup>
</enhancement>
<enhancement>
<descriptorgroup>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
aged
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
article
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
electrode
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
female
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
heart atrium
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
heart pacing
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
heart ventricle
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
human
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
implantation
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
longevity
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
major clinical study
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
male
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
medical instrumentation
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
survival
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
treatment indication
</mainterm>
</descriptor>
</descriptors>
</descriptorgroup>
<classificationgroup>
<classifications type="ASJC">
<classification>
<classification-code>
1314
</classification-code>
</classification>
<classification>
<classification-code>
2705
</classification-code>
</classification>
</classifications>
</classificationgroup>
<manufacturergroup>
<manufacturers type="MNV">
<manufacturer country="usa">
Intermedics
</manufacturer>
</manufacturers>
</manufacturergroup>
<tradenamegroup>
<tradenames type="TNV">
<trademanuitem>
<tradename>
ThinLine bipolar pacing lead
</tradename>
<manufacturer country="usa">
Intermedics
</manufacturer>
</trademanuitem>
</tradenames>
</tradenamegroup>
</enhancement>
<enhancement>
<descriptorgroup>
<descriptors type="DRG" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
C reactive protein
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
fibrinogen
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
heat shock protein 60
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
high density lipoprotein cholesterol
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
roxithromycin
</mainterm>
<link>
drug therapy
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
triacylglycerol
</mainterm>
<link>
endogenous compound
</link>
</descriptor>
</descriptors>
<descriptors type="MED" controlled="y">
<descriptor>
<mainterm weight="b" candidate="n">
angiography
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
atherosclerosis
</mainterm>
<link>
etiology
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
bacterium isolation
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
chlamydiasis
</mainterm>
<link>
drug therapy
</link>
</descriptor>
<descriptor>
<mainterm weight="a" candidate="n">
Chlamydophila pneumoniae
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
controlled study
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
disease association
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
endothelium injury
</mainterm>
<link>
diagnosis
</link>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
human
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
human cell
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
human tissue
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
immunoregulation
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
pathogenesis
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
priority journal
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
review
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
risk factor
</mainterm>
</descriptor>
<descriptor>
<mainterm weight="b" candidate="n">
seroepidemiology
</mainterm>
</descriptor>
</descriptors>
</descriptorgroup>
<classificationgroup>
<classifications type="ASJC">
<classification>
<classification-code>
2705
</classification-code>
</classification>
</classifications>
</classificationgroup>
<chemicalgroup>
<chemicals source="esbd">
<chemical>
<chemical-name>
9001-32-5
</chemical-name>
<cas-registry-number>
fibrinogen
</cas-registry-number>
</chemical>
</chemicals>
<chemicals source="esbd">
<chemical>
<chemical-name>
9007-41-4
</chemical-name>
<cas-registry-number>
C reactive protein
</cas-registry-number>
</chemical>
</chemicals>
<chemicals source="esbd">
<chemical>
<chemical-name>
80214-83-1
</chemical-name>
<cas-registry-number>
roxithromycin
</cas-registry-number>
</chemical>
</chemicals>
</chemicalgroup>
</enhancement>
</root>