#!/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 order
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..$#$OrderTheseFirst) , 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
    }	
}