Words blacklist matches to patterns instead of words

I have a words blacklist rule that matches the word "and" in the first name to keep people from trying to register more than one person on a single form. However, I got a complaint about a registration being rejected and the first name field being highlighted in red when someone named "Wanda" tried to register.

I think the words blacklist rule is matching to a pattern instead of a word.

      case "blacklist":
          $blacklist = explode(',', $rule['data']);
          $blacklist = array_map('trim', $blacklist);
          $blacklist_regex = implode('|', $blacklist);
          foreach ($items as $key => $val) {
            if ($val != '' && (preg_match("/$blacklist_regex/i", $val))) {
              $errors[$key] = _webform_validation_i18n_error_message($rule);
            }
          }
        return $errors;
        break;

It think you need to add "\b"`s around to the regex pattern to do a word matching:

preg_match("/\b$blacklist_regex\b/i", $val)