use HTML::HTML5::Parser;
use XML::LibXML 1.94;
use XML::LibXML::QuerySelector;

my $document = HTML::HTML5::Parser->load_html(IO => \*DATA);
$document
	-> querySelectorAll('h1, h2')
	-> foreach(sub { $_->setNodeName('div') });
	
print $document->toString;

__DATA__
<ol id="intelliTxt" class="steps">
	<li class="section">
		<h2 class="header Heading3">Clear Up Those Blackheads</h2>
		<ul>
			<li class="step ">
				<span class="stepNumber">1</span>