In lieu of embedded-files-related examples, quite a few others distribution provides might be considered "suitable" to study, especially considering "Internals" and "Reference" (warning: 53 Mb PDF).

use strict;
use warnings;
use feature 'say';
use Data::Dump;
use Encode 'decode';
use CAM::PDF;

my $doc = CAM::PDF-> new( 'test.pdf' ) or die;

dd get_embedded_files( $doc );

# Get a hashref. Keys (filenames) may happen to be encoded as 
# UTF16-BE, with prepended BOM. Sort it out yourself, if names 
# are relevant at all.

sub get_embedded_files {
    my $doc        = shift;
    my $names_dict = $doc-> getValue( $doc-> getRootDict-> { Names }) 
+or return {};
    my $files_tree = $names_dict-> { EmbeddedFiles }                  
+or return {};
    my @agenda     = $files_tree;
    my $ret        = {};

# Hardly ever more than single leaf, but...

    while ( @agenda ) {
        my $item = $doc-> getValue( shift @agenda );

        if ( $item-> { Kids }) {
            my $kids = $doc-> getValue( $item-> { Kids });
            push @agenda, @$kids
        }
        else {
            my $nodes = $doc-> getValue( $item-> { Names });
            my @names = map { $doc-> getValue( $_ )} @$nodes;
            while ( @names ) {
                my ( $k, $v ) = splice @names, 0, 2;
                my $ef_node   = $v-> { EF };
                my $ef_dict   = $doc-> getValue( $ef_node );
                my $any_num   = ( values %$ef_dict )[ 0 ]-> { value };
                my $obj_node  = $doc-> dereference( $any_num );
                $ret-> { $k } = $doc-> decodeOne( $obj_node-> { value 
+}, 0 );
            }
        }
    }
    return $ret
}
[download]

If it looks unpleasant and complex, then it is. "getValue" everywhere may lead to slight temporary madness in larger projects.

I only tested it against couple of my files. If anything is broken, here's a backup brute force solution (since files are probably simple and overhead tiny) -- just enumerate all objects, one of them will be yours.

use strict;
use warnings;
use feature 'say';
use CAM::PDF;
use XML::LibXML;

my $doc = CAM::PDF-> new( 'test.pdf' ) or die;
$doc-> cacheObjects;

while ( my ( $k, $v ) = each %{ $doc-> { objcache }}) {
    next unless $v-> { value }{ type } eq 'dictionary' and
                $v-> { value }{ value }{ StreamData };
    my $str = $doc-> decodeOne( $v-> { value }, 0 );
    my $dom = eval { XML::LibXML-> load_xml( string => $str )};
    next unless $dom;
    
# Process expected XML, skip possible others (Adobe XMP, etc.)
# ...

}
[download]