Функция разбивающая строку на пары

(defun pairs (lst)
(loop while ((AND (cdr lst) (cddr lst))) do ( (setq newlst (cons  newlst (list (car x) (cadr x))))
                                                               (setq lst (cddr lst))))
      if (null (cdr lst)) (setq newlst (cons nelst (list (car lst))))  (setq newlst (cons newlst (list (car lst) (cadr lst)))))

(defun f (l)
  (loop
     for (a b) on l by #'cddr
     while b ;; nil?
     collect (list a b)))

(defun f (l)
  (loop
     for n = 0 then (+ 2 n)
     for f = (nth n l)
     for s = (nth (1+ n) l)
     while s
     collect (list f s)))

(defun f (l)
  (let (r)
    (do ((first (first l) (first rest))
     (second (second l) (second rest))
     (rest (cddr l) (cddr rest)))
    ((null rest) (nreverse r))
      (push (list first second) r))))

(defun f (l)
  (let (#'nil buff)
    (dolist (v l `(,@(nreverse function) ,(nreverse buff)))
      (cond
    ((= (length buff) 2)
     (push (nreverse buff) function)
     (setf buff (list v)))
    ((push v buff))))))

(defun pair (w &aux (b (car w)))
  (loop for a in (cdr w)
        when b collect (list b a) into z
        do (if b (setf b nil) (setf b a))
        finally (return (if b (append z `((,b))) z))))
 
> (pair '(a b c d e f))
((A B) (C D) (E F))
> (pair '(a b c d e))
((A B) (C D) (E))

(defun pair (w)
  (loop for (a b) on w by #'cddr
        if b collect (list a b)
        else collect (list a)))
 
> (pair '(a b c d e f))
((A B) (C D) (E F))
> (pair '(a b c d e))
((A B) (C D) (E))

(defun pair (w)
  (loop for (a b) on w by #'cddr
        collect (if b (list a b) (list a))))
 
> (pair '(a b c d e f))
((A B) (C D) (E F))
> (pair '(a b c d e))
((A B) (C D) (E))

(defun pair (w)
  (loop for (a b) on w by #'cddr
        collect (if b `(,a ,b) `(,a))))
 
> (pair '(a b c d e f))
((A B) (C D) (E F))
> (pair '(a b c d e))
((A B) (C D) (E))