Yep and illustrates nicely why handling HTML with regexes is not recommended. Anyway, I think the following works:

sub is_all_in_bold {
    my $title=shift;
    my ($title_content)=$title=~m!<title>(.*?)</title>!s;
    1 while $title_content=~s#<b>(?:[^<>]+|(?!</?b>).)*</b>##s;
    print "$title_content\n";
    return !$title_content;
}

while (<DATA>) {
    print;
    chomp;
    next unless /\S/;
    print is_all_in_bold($_) ? "Its all in bold\n" : "Its not all in b
+old\n";
}
__END__
<title><b>Meta&hyphen;Ethics and The Problem of Creeping Minimalism</b
+></title>
<title>Meta&hyphen;Ethics and <b>The Problem of Creeping</b> <b>Minima
+lism</b></title>
<title><b>foo<b>bar</b></b></title>
[download]