anchor.diff:   * `<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
  + * `!`: insert command output before each selection
  + * `<a-!>`: append command output after each 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
  + * `&`: align selections, 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
  
positive.code:  * `~`: 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.
  
   * `<a-)>`: rotate selections content, if specified, the count groups
              selections, so `3<a-)>` rotate (1, 2, 3) and (4, 5, 6)
  
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
  
  