Fix regexp mistakes

* lisp/progmodes/cperl-mode.el (cperl--package-regexp):
Avoid double repetition; cperl--ws-or-comment-regexp is already
repeated with 1+.
* test/lisp/textmodes/dns-mode-tests.el
(dns-mode-tests-dns-mode-soa-increment-serial): Escape literal '$'.
* test/lisp/emacs-lisp/rx-tests.el (rx-regexp): Modify test to not
trigger a linting warning while retaining its testing power.

lisp/progmodes/cperl-mode.el

@@ -1305,7 +1305,7 @@ is a legal variable name).")
      (group (regexp ,cperl--normal-identifier-regexp))
      (opt
       (sequence
-       (1+ (regexp ,cperl--ws-or-comment-regexp))
+       (regexp ,cperl--ws-or-comment-regexp)
        (group (regexp ,cperl--version-regexp))))))
   "A regular expression for package NAME VERSION in Perl.
 Contains two groups for the package name and version.")

test/lisp/emacs-lisp/rx-tests.el

@@ -388,11 +388,11 @@
 (ert-deftest rx-regexp ()
   (should (equal (rx (regexp "abc") (regex "[de]"))
                  "\\(?:abc\\)[de]"))
+  (should (equal (rx "a" (regexp "$"))
+                 "a\\(?:$\\)"))
   (let ((x "a*"))
     (should (equal (rx (regexp x) "b")
                    "\\(?:a*\\)b"))
-    (should (equal (rx "a" (regexp "*"))
-                   "a\\(?:*\\)"))
     (should (equal (rx "" (regexp x) (eval ""))
                    "a*"))))
 

test/lisp/textmodes/dns-mode-tests.el

@@ -37,7 +37,7 @@
     (dns-mode-soa-increment-serial)
     ;; Number is updated from 2015080302 to the current date
     ;; (actually, just ensure the year part is later than 2020).
-    (should (string-match "$TTL 86400
+    (should (string-match "\\$TTL 86400
 @   IN  SOA     ns.icann.org. noc.dns.icann.org. (
         20[2-9][0-9]+  ;Serial
         7200        ;Refresh