Using XML::LibXML and Template:

#!/usr/bin/perl
use warnings;
use strict;

use XML::LibXML;
use Template;

my $xpc = 'XML::LibXML::XPathContext'->new;
$xpc->registerNs(a => 'http://www.w3.org/2005/Atom');
$xpc->registerNs(y => 'http://www.youtube.com/xml/schemas/2015');
$xpc->registerNs(m => 'http://search.yahoo.com/mrss/');

my $dom = 'XML::LibXML'->load_xml(location => 'videos.xml');

my $title = $xpc->findvalue('/a:feed/a:title', $dom);
my $name  = $xpc->findvalue('/a:feed/a:author/a:name', $dom);

my $entries;
for my $entry ($xpc->findnodes('/a:feed/a:entry', $dom)) {
    my $title       = $xpc->findvalue('a:title', $entry);
    my $url         = $xpc->findvalue('a:link/@href', $entry);
    my $description = $xpc->findvalue('m:group/m:description', $entry)
+;
    push @$entries, {url         => $url,
                     title       => $title,
                     description => $description || '--'};
}

binmode *DATA, ':encoding(UTF-8)';
my $template = do { local $/; <DATA> };
my $tt = 'Template'->new;
binmode *STDOUT,  ':encoding(UTF-8)';
$tt->process(\$template, {title   => $title,
                          name    => $name,
                          entries => $entries});

__DATA__
<h3>[% title %]</h3>

<b>[% name %]</b>

<ul>
[% FOR entry IN entries %]
<li> [[% entry.url %]|[% entry.title | html %]]
<p><i>[% entry.description | html %]
</i></p></li>
[% END %]
</ul>
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