use strict;
use warnings;
use feature 'say';

use XML::LibXML;

my $xml = XML::LibXML->createDocument();
my $r   = $xml->createElement('root');
$xml->setDocumentElement($r);
$r->addChild($xml->createTextNode('<&'));
say $xml->toString;
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create root ;
insert text '<&' into /root ;
ls . ;
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With XML::LibXML, you can get away without creating a document and element...

print XML::LibXML::Text->new('<&')->toString;
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It's pretty easy to wrap that up into a function:

sub escape_xml {
  XML::LibXML::Text->new(shift)->toString
}

print escape_xml('<&');
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perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

Well, yes. I was just discreetly suggesting creating the whole packages in XML::LibXML.