anchor.diff:   * `~`: to upper case
    * ``<a-`>``: swap case
   
  - * `@`: convert tabs to spaces in current selections, uses the buffer
  -        tabstop option or the count parameter for tabstop.
  - * `<a-@>`: convert spaces to tabs in current selections, uses the buffer
  -            tabstop option or the count parameter for tabstop.
  + * `@`: convert selected tabs to spaces, uses the buffer tabstop option or
  +        the count parameter for tabstop.
  + * `<a-@>`: convert selected spaces to tabs, uses the buffer tabstop option
  +            or the count parameter for tabstop.
   
    * `<a-)>`: rotate selections content, if specified, the count groups
               selections, so `3<a-)>` rotate (1, 2, 3) and (4, 5, 6)
  
positive.code:  * `<a-|>`: pipe each selection through the given external filter program
          and ignore its output
  
   * `!`: insert command output before selection
   * `<a-!>`: append command output after selection
  
   * `u`: undo last change
   * `<a-u>`: move backward in history
   * `U`: redo last change
   * `<a-U>`: move forward in history
  
   * `&`: align selection, align the cursor of selections by inserting
          spaces before the first character of the selection
   * `<a-&>`: copy indent, copy the indentation of the main selection
          (or the count one if a count is given) to all other ones
  
negative.code: Changes
  ~~~~~~~
  
   * `i`: enter insert mode before each selection
   * `a`: enter insert mode after each selection
   * `d`: yank and delete each selection
   * `c`: yank and delete each selection and enter insert mode
   * `.`: repeat last insert mode change (`i`, `a`, or `c`, including
          the inserted text)
  
   * `<a-d>`: delete each selection
   * `<a-c>`: delete each selection and enter insert mode
  
   * `I`: enter insert mode at each selection begin line start
   * `A`: enter insert mode at each selection end line end
   * `o`: enter insert mode in one (or given count) new lines below
          each selection end
   * `O`: enter insert mode in one (or given count)  new lines above
          each selection begin
  
   * `<a-o>`: add an empty line below each cursor
   * `<a-O>`: add an empty line above each cursor
  
   * `y`: yank selections
   * `p`: paste after each selection end
   * `P`: paste before each selection begin
   * `<a-p>`: paste all after each selection end
   * `<a-P>`: paste all before each selection begin
   * `R`: replace each selection with yanked text
   * `<a-R>`: replace each selection with every yanked text
  
   * `r`: replace each character with the next entered one
  
  