use strict;
use warnings;
use HTML::TokeParser;

my @tags = @ARGV;
@tags || die "Give a list of tags to retain.\n";
my %keep = map { lc($_) => 1, lc("/$_") => 1 } @tags;

my $p = HTML::TokeParser->new(\*DATA);

while ( my $t = $p->get_token )
{
    if ( $t->[0] =~ /S|E/ and $keep{$t->[1]} )
    {
        print $t->[-1];
    }
    elsif ( $t->[0] eq 'T' )
    {
        print $t->[1];
    }
}

__DATA__
<div>
    <h1>Bang!<sup>1</sup></h1>
    <p>Did <i>italic</i> and <a href="/uri">link with <b>bold</b>
       inside it</a>.</p>
 <a href="/top-level">naked link</a>
    <p><i>The</i> <b>content</b> of the body <sup>element</sup> is
       displayed in your <span>browser</span>.</p>
</div>

##</code><code>##

use warnings;
use strict;
use XML::LibXML;

my @strip = @ARGV;
@strip || die "Give a list of tags to strip.\n";

my $parser = XML::LibXML->new();
$parser->line_numbers(1);

my $raw = join '', <DATA>;
my $doc = $parser->parse_html_string($raw);

my $root = $doc->documentElement();

for my $strip ( @strip )
{
    for my $node ( $root->findnodes("//$strip") )
    {
        my $fragment = $doc->createDocumentFragment();
        $fragment->appendChild($_) for $node->childNodes;
        $node->replaceNode($fragment);        
    }
}

print $doc->serialize(1);

__END__
<div>
    <h1>Bang!<sup>1</sup></h1>
    <p>Did <i>italic</i> and <a href="/uri">link with <b>bold</b>
       inside it</a>.</p>
 <a href="/top-level">naked link</a>
    <p><i>The</i> <b>content</b> of the body <sup>element</sup> is
       displayed in your <span>browser</span>.</p>
</div>