Not exactly the order you specified in the example, but a correct order anyway:

use strict;
use warnings;
no warnings 'uninitialized';

use XML::Rules;

my %written;
my %depends;
my $parser = XML::Rules->new(
    style => 'filter',
    rules => {
        _default => 'raw',
        'name,members' => 'raw extended',
        'Group' => 'raw extended array',
        record => sub {
            my @I_depend;
            if (exists $_[1]->{':members'} and exists $_[1]->{':member
+s'}{':Group'}) {
                @I_depend = grep !exists $written{$_}, map $_->{_conte
+nt}, @{$_[1]->{':members'}{':Group'}};
            }
            if (@I_depend) {
                $_[1]->{':I_depend'} = {map {$_ => 1} @I_depend};
                foreach (@I_depend) {
                    push @{$depends{$_}}, $_[1]
                }
                return;
            } else {
                my $name = $_[1]->{':name'}{_content};
                $written{$name} = 1;
                my @to_write = $_[1];
                if (exists $depends{$name}) {
                    push @to_write, find_dependent($name);
                }
                return 'record' => \@to_write;
            }
        }
    }
);

sub find_dependent {
    my $name = shift;
    my @to_write;
    foreach my $parent (@{$depends{$name}}) {
        delete $parent->{':I_depend'}{$name};
        if (! %{$parent->{':I_depend'}}) { # if it doesn't depend on a
+nything more
            push @to_write, $parent;
            push @to_write, find_dependent($parent->{':name'}{_content
+});
        }
    }
    delete $depends{$name};
    return @to_write;
}

$parser->filter(\*DATA);

if (%depends) {
    print STDERR "Unsatisfied dependencies! Some records depend on the
+se unknown groups: ",
        join ", ", keys %depends;
}
[download]

Only if all the records depend (directly or indirectly) on the last one, will the script keep at one moment all the data in memory. Otherwise whenever it finds a record with no dependencies or whose all dependencies were already printed, it will print that record and all records that only depended on this one (and those already printed).

---

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