use strict;
use XML::Rules;

my $reader = XML::Rules->new(
	rules => {
		_default => 'raw',
		head => 'content array',
		TEI => 'pass no content',
	}
);

my $heads = $reader->parsefile( $small_file_name )->{head};
#use Data::Dumper;
#print Dumper($heads);

##</code><code>##

my $updater = XML::Rules->new(
	style => 'filter',
	rules => {
		_default => 'raw',
		head => sub {
			my ($tag, $attr) = @_;
			$attr->{_content} = shift(@$heads);
			return $tag => $attr;
		}
	}
);

$updater->filterfile( $big_file_name, $updated_big_file_name);