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------------------------------------------------------------------------

In Org 9.7.3, the variables bound using the =#+BIND= keyword have values that
are nested.  E.g., when a string value is provided, the value actually gets set
to a singleton list containing said string.  This can be observed using the
snippet:

#+name: bugs/org/9.7/bind-vars
#+header: :tangle /tmp/ox-bind-variable-mre.el
#+begin_src emacs-lisp :lexical t
  ;; -*- lexical-binding: t; no-byte-compile: nil; -*-

  (require 'ox)
  (require 'ox-org)

  (let ((org-export-allow-bind-keywords t)
        (org-confirm-babel-evaluate nil))
    (princ (format "%s\n" (org-version)))
    (princ (format "%s"
                   (org-export-string-as "#+BIND: my/bug/ox/foo \"foo\"
  ,#+BIND: my/bug/ox/bar

  ,#+begin_src emacs-lisp :exports results :results output
    (princ (format \"%s = '%s' :: %s\n\" \"my/bug/ox/foo\" my/bug/ox/foo (type-of my/bug/ox/foo)))
    (princ (format \"%s = '%s' :: %s\n\" \"my/bug/ox/bar\" my/bug/ox/bar (type-of my/bug/ox/bar)))
  ,#+end_src"
                                         'org
                                         t))))
#+end_src

#+RESULTS: bugs/org/9.7/bind-vars
: #+bind: my/bug/ox/foo "foo"
: #+bind: my/bug/ox/bar
: 
: #+results: 
: : my/bug/ox/foo = '(foo)' :: cons
: : my/bug/ox/bar = 'nil' :: symbol

The bug is in the definition of ~org-export--set-variables~.  By fixing the
issue in ~org-export--set-variables~ we get the expected values set:

#+begin_src emacs-lisp :lexical t :noweb yes
  ;; -*- lexical-binding: t; no-byte-compile: nil; -*-
  (require 'org)
  (require 'ox)

  (defun org-export--set-variables (variable-alist)
    "Set buffer-local variables according to VARIABLE-ALIST in current buffer."
    (pcase-dolist (`(,var . ,val) variable-alist)
      (set (make-local-variable var) (car val))))

  <<bugs/org/9.7/bind-vars>>
#+end_src

#+RESULTS:
: #+bind: my/bug/ox/foo "foo"
: #+bind: my/bug/ox/bar
: 
: #+results: 
: : my/bug/ox/foo = 'foo' :: string
: : my/bug/ox/bar = 'nil' :: symbol


The patch is attached below.