Before we would separate categories with a "-" (single dash), but that
could lead to confusion because the field separator is a "--" (double
dash).  Now the separator is the plus sign.

What follows are instructions to update existing entries.  Apologies for
the inconvenience, as I am not aware of a better way to handle this
case.

* * *

Refactor all your USLS files (WARNING---only tested with Emacs 29):

+ BACK UP ALL YOUR FILES (unless you are already tracking them with git,
  in which case double-check the following changes before committing).

+ Go to the USLS directory (if there are subdirectories, repeat this
  step for each of them).

+ Make Dired editable with `C-x C-q`

+ Start recording a keyboard macro with `F3`, `C-x (` or `M-x kmacro-start-macro`.

+ Type `M-:` and evaluate:

  ```elisp
  (progn
    (goto-char (point-min))
    (if-let* ((end (search-forward-regexp "--\\([0-9A-Za-z_-]*-[0-9A-Za-z_-]*\\)--" nil t))
              (beg (search-bac...