use strict;
use warnings;

# creating my object with a sortorder
my $xs = new MyXMLSimple(
    XMLDecl => '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>',
    KeepRoot => 1,
    KeyAttr => [ ],
    SortOrder => {
        supertag => [qw[
            tag1
            tag3
            tag4
            tag10
        ]],
    },
);

# Some testdata
my $structure = {
    supertag => {
        tag10 => { content => 'value 2',  },
        tag3 =>  { content => 'value 3',  },
        tag1 =>  { content => 'value 1',  },
        tag91 => { content => 'value 91', },
        tag90 => { content => 'value 90', },
        tag4 =>  { content => 'value 4',  },
    }
};

print $xs->XMLout($structure);

################################################################################
package MyXMLSimple;      # my XML::Simple subclass 
use base 'XML::Simple';
use Carp;

sub new {
    my $class= shift;
    if(@_ % 2) {
        croak "Default options must be name=>value pairs (odd number supplied)";
    }
    my %raw_opt = @_;
    # removing my new option from the options supplied
    my $sortorder= delete $raw_opt{'SortOrder'};
    # creating the XML::Simple element
    my $self= $class->SUPER::new( %raw_opt );
    # adding the sortorder in
    $self->{'SortOrder'}= $sortorder;
    return (bless($self, $class));
}

# Overriding the method here
sub sorted_keys
{
   my ($self, $name, $hashref) = @_;
   # check whether we have a sortorder for $name
   my $ordered= $self->{'SortOrder'}->{$name};
   if ($ordered) {
      # if so, prepare the sortorder
      my %ordered_hash;
      @ordered_hash{@$ordered} = ();

      #set ordered tags in front of others
      return
        grep {exists $hashref->{$_}} @$ordered,
        grep {not exists $ordered_hash{$_}} $self->SUPER::sorted_keys($name, $hashref);
   }
   return $self->SUPER::sorted_keys($name, $hashref); # for the rest, I don't care!
}