Warning from CMUCL 19a about CL-PPCRE 0.9.0 usage

I'm seeing some warnings from CMUCL that I don't understand. Here is the warning the simplest code I've written at the moment that produces the warning:

(defun flurp (line)
(let (delta)
    (register-groups-bind (delta-str)
        ('(:sequence (:register (:greedy-repetition 1 nil :digit-class)))
          line)
      (setq delta (parse-integer delta-str)))))

and the warning:

; In: DEFUN FLURP

;   (REGISTER-GROUPS-BIND (DELTA-STR) ('# LINE) (SETQ DELTA #))
; --> LET MULTIPLE-VALUE-BIND MULTIPLE-VALUE-CALL FUNCTION WHEN COND IF PROGN
; --> LET* LET
; ==>
;   (IF #:START-INDEX5
;       (FUNCALL #:SUBSTR-FN6 #:TARGET-STRING0 #:START-INDEX5 #)
;       NIL)
; Warning: This is not a (VALUES &OPTIONAL BASE-STRING &REST T):
;   NIL
; ; [Last message occurs 2 times]

What follows are a few more examples, with SSMT-OUTPUT-SUMMARY being the original snippet.

(in-package #:pg-user)

(defun ssmt-output-summary (pname)
(with-open-file (in pname :direction :input)
    (loop with line = nil
          and delta = 0 and added = 0 and changed = 0 and deleted = 0
          while (setq line (read-line in nil))
          when (register-groups-bind
                      (delta-str added-str changed-str deleted-str)
                    ('(:sequence
                       "__UNDEF__"
                       (:greedy-repetition 1 nil :whitespace-char-class)
                       ;; Delta SLOC
                       (:register (:greedy-repetition 1 nil :digit-class))
                       (:greedy-repetition 1 nil :whitespace-char-class)
                       ;; Skip over delta AELOC
                       (:greedy-repetition 1 nil :digit-class)
                       (:greedy-repetition 1 nil :whitespace-char-class)
                       ;; Code added
                       (:register (:greedy-repetition 1 nil :digit-class))
                       (:greedy-repetition 1 nil :whitespace-char-class)
                       ;; Code changed
                       (:register (:greedy-repetition 1 nil :digit-class))
                       (:greedy-repetition 1 nil :whitespace-char-class)
                       ;; Code deleted
                       (:register (:greedy-repetition 1 nil :digit-class)))
                      line)
                  ;; Somebody doesn't like our attempting to return
                  ;; multiple values past the REGISTER-GROUPS-BIND
                  (setq delta (parse-integer delta-str)
                        added (parse-integer added-str)
                        changed (parse-integer changed-str)
                        deleted (parse-integer deleted-str)))
          do (return (values delta added changed deleted))
          finally (warn "Could not find summary for ~A" pname))))

(defun foo (line)
(let (delta added changed deleted)
    (register-groups-bind
          (delta-str added-str changed-str deleted-str)
        ('(:sequence
           "__UNDEF__"
           (:greedy-repetition 1 nil :whitespace-char-class)
           ;; Delta SLOC
           (:register (:greedy-repetition 1 nil :digit-class))
           (:greedy-repetition 1 nil :whitespace-char-class)
           ;; Skip over delta AELOC
           (:greedy-repetition 1 nil :digit-class)
           (:greedy-repetition 1 nil :whitespace-char-class)
           ;; Code added
           (:register (:greedy-repetition 1 nil :digit-class))
           (:greedy-repetition 1 nil :whitespace-char-class)
           ;; Code changed
           (:register (:greedy-repetition 1 nil :digit-class))
           (:greedy-repetition 1 nil :whitespace-char-class)
           ;; Code deleted
           (:register (:greedy-repetition 1 nil :digit-class)))
          line)
      (setq delta (parse-integer delta-str)
            added (parse-integer added-str)
            changed (parse-integer changed-str)
            deleted (parse-integer deleted-str)))))

(defun bar (line)
(register-groups-bind
        (delta-str added-str changed-str deleted-str)
      ('(:sequence
         "__UNDEF__"
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Delta SLOC
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Skip over delta AELOC
         (:greedy-repetition 1 nil :digit-class)
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code added
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code changed
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code deleted
         (:register (:greedy-repetition 1 nil :digit-class)))
        line)
    (declare (ignore delta-str added-str changed-str deleted-str))))

(defun baz (line)
(register-groups-bind
        (delta-str added-str changed-str deleted-str)
      ('(:sequence
         "__UNDEF__"
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Delta SLOC
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Skip over delta AELOC
         (:greedy-repetition 1 nil :digit-class)
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code added
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code changed
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code deleted
         (:register (:greedy-repetition 1 nil :digit-class)))
        line)
    (declare (ignore added-str changed-str deleted-str))
    delta-str))

(defun blatz (line)
(register-groups-bind
        (delta-str added-str changed-str deleted-str)
      ('(:sequence
         "__UNDEF__"
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Delta SLOC
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Skip over delta AELOC
         (:greedy-repetition 1 nil :digit-class)
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code added
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code changed
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code deleted
         (:register (:greedy-repetition 1 nil :digit-class)))
        line)
    (values delta-str added-str changed-str deleted-str)))

(defun blurp (line)
(register-groups-bind
        (delta-str added-str changed-str deleted-str)
      ('(:sequence
         "__UNDEF__"
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Delta SLOC
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Skip over delta AELOC
         (:greedy-repetition 1 nil :digit-class)
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code added
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code changed
         (:register (:greedy-repetition 1 nil :digit-class))
         (:greedy-repetition 1 nil :whitespace-char-class)
         ;; Code deleted
         (:register (:greedy-repetition 1 nil :digit-class)))
        line)
    (declare (ignore delta-str added-str changed-str deleted-str))
    69))

And the complaints during compilation.

* (lisp-implementation-version)
"19a"
* (lisp-implementation-type)
"CMU Common Lisp"
* (software-version)
"5.8"
* (software-type)
"SunOS"
* (compile-file "/home/kick/tmp/scratch.lisp")
; Python version 1.1, VM version UltraSparc/Solaris 7 on 19 NOV 04 01:59:21 pm.
; Compiling: /home/kick/tmp/scratch.lisp 19 NOV 04 01:58:23 pm

; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE "__UNDEF__" # ...)):
; Converted SSMT-OUTPUT-SUMMARY.
; Compiling DEFUN SSMT-OUTPUT-SUMMARY:

;
;
; File: /home/kick/tmp/scratch.lisp

; In: DEFUN SSMT-OUTPUT-SUMMARY

;   (REGISTER-GROUPS-BIND (DELTA-STR ADDED-STR CHANGED-STR DELETED-STR)
;                         ('# LINE)
;                         (SETQ DELTA # ADDED # ...))
; --> LET MULTIPLE-VALUE-BIND MULTIPLE-VALUE-CALL FUNCTION WHEN COND IF PROGN
; --> LET* LET
; ==>
;   (IF #:START-INDEX15
;       (FUNCALL #:SUBSTR-FN16 #:TARGET-STRING10 #:START-INDEX15 #)
;       NIL)
; Warning: This is not a (VALUES &OPTIONAL BASE-STRING &REST T):
;   NIL
; ; [Last message occurs 8 times]

; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE "__UNDEF__" # ...)):
; Converted FOO.
; Compiling DEFUN FOO:

;
;
; File: /home/kick/tmp/scratch.lisp

; In: DEFUN FOO

;   (REGISTER-GROUPS-BIND (DELTA-STR ADDED-STR CHANGED-STR DELETED-STR)
;                         ('# LINE)
;                         (SETQ DELTA # ADDED # ...))
; --> LET MULTIPLE-VALUE-BIND MULTIPLE-VALUE-CALL FUNCTION WHEN COND IF PROGN
; --> LET* LET
; ==>
;   (IF #:START-INDEX5
;       (FUNCALL #:SUBSTR-FN6 #:TARGET-STRING0 #:START-INDEX5 #)
;       NIL)
; Warning: This is not a (VALUES &OPTIONAL BASE-STRING &REST T):
;   NIL
; ; [Last message occurs 8 times]

; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE "__UNDEF__" # ...)):
; Converted BAR.
; Compiling DEFUN BAR:
; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE "__UNDEF__" # ...)):
; Converted BAZ.
; Compiling DEFUN BAZ:
; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE "__UNDEF__" # ...)):
; Converted BLATZ.
; Compiling DEFUN BLATZ:
; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE "__UNDEF__" # ...)):
; Converted BLURP.
; Compiling DEFUN BLURP:
; Compiling Load Time Value of (CREATE-SCANNER '(:SEQUENCE #)):
; Converted FLURP.
; Compiling DEFUN FLURP:

;
;
; File: /home/kick/tmp/scratch.lisp

; In: DEFUN FLURP

; Byte Compiling Top-Level Form:

; Compilation unit finished.
; 18 warnings

; /home/kick/tmp/scratch.sparcf written.
; Compilation finished in 0:00:02.

#p"/home/kick/tmp/scratch.sparcf"
T
T
*

I don't understand why only SSMT-OUTPUT-SUMMARY, FOO, and FLURP are the only ones with warnings.

--
Damien Kick