You can use the following-sibling and preceding-sibling axes.

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use XML::LibXML;

my $dom = 'XML::LibXML'->load_xml(location => shift);
my $root = $dom->getDocumentElement();

my ($bfm) = $root->findnodes('//breakfast_menu');
say for $bfm->findnodes('(following-sibling::* | preceding-sibling::*)
+');
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