In this post there was good advice: Re^2: XML::Simple how do i keep the same xml format (Values and Attributs)?

UPDATE: Only way I see is to create 4 XML files for the second level in your tree according to the desired order, and then manually create the outer structure around them. For example:

use strict;
use warnings;
use XML::Simple;
my $TGROUP = { 
     COLS    => 4,
     COLSPEC => [ 1, 2, 3, 4 ],
     THEAD   => { head => "head" },
     TBODY   => { body => "body" },
};
print "<TABLE>\n";
for ( qw( COLS COLSPEC THEAD TBODY ) ) { # in your desired order
     print XMLout( {$_ => $TGROUP->{$_}}, RootName => $_, KeepRoot => 
+1, NoATTR => 1 );
}
print "</TABLE>\n";
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