$data =~ s{(<a\s(?:[^>](?!href))*href\s*)(&(&[^;]+;)?(?:.(?!\3))+(?:\3)?)([^>]+>)}
 {$1.decode_entities($2).$4}gsei;

##</code><code>##

<p class="foo" name="bar">
<p name="bar" CLASS="ovid has no class">
<p NAME="bar" class="ovid has no class">
<p name="bar" class="ovid has no class">

##</code><code>##

package HTML::Token;

sub new {
    my ($class,$token) = @_;
    my $self = bless { token => $token }, $class;
    my $identifier = $self->identifier;
    return $self;
}

sub identifier {
    my $self  = shift;
    my $token = $self->{token};
    my $attributes = $token->return_attrseq;
    my $tag = $token->return_tag;
    if (ref $attributes eq 'ARRAY') {
        return sprintf "%s %s", $tag, join ' ', sort @$attributes;
    }
    else {
        return $tag;
    }
}

##</code><code>##

my $html = <<END_HTML;
<h1>This is a test</h1>
<p class="foo" name="bar">so what???
END_HTML
my $parser = HTML::TokeParser::Simple->new(\$html);
my @tokens = ();
while (my $token = $parser->get_tag) {
    push @tokens => HTML::Token->new($token);
}
push @tokens => (qw[* . *]); # make the (p) tag zero or more, followed by anything

##</code><code>##

use Token::Regex;
my $regex = Token::Regex->new('HTML::Token');
$regex->parse(\@tokens);

##</code><code>##

my $tokens = html_tokens(<<END_HTML);
<h1>This is html</h1>
<p name="bar" CLASS="ovid has no class">so what???
<p NAME="bar" class="ovid has no class">so what???
<p name="bar" class="ovid has no class">so what???
<h2>and this is okay</h2>
END_HTML

if ($regex->match($tokens)) {
    print "Yes\n";
}
else {
    print "No\n";
}

$tokens = html_tokens(<<END_HTML);
<p name="bar" CLASS="ovid has no class">so what???
<p NAME="bar" class="ovid has no class">so what???
<p name="bar" class="ovid has no class">so what???
<h2>and this is okay</h2>
END_HTML

if ($regex->match($tokens)) {
    print "Yes\n";
}
else {
    print "No\n";
}


sub html_tokens {
    my $html = shift;
    
    my $parser = HTML::TokeParser::Simple->new(\$html);
    my @tokens;
    while (my $token = $parser->get_tag) {
        push @tokens => HTML::Token->new($token);
    }
    return \@tokens;
}