* They swap the default order of skipping characters.
  For positive arguments: first non-word chars, then word chars.
* This is especially useful after executing the non-at-modified versions.
  For instance, at the beginning of a word, `@W` jumps to its end.
  `@V` would delete the remainder of the word.
* Since they have to evaluate the at-modifier, which has syntactic
  significance, the command implementations can no longer use
  transition tables, so they are in the switch-statements instead.

* All the movement commands have shortcuts for their negative forms:
  `R` instead of `-C`, `B` instead of `-L`.
  Therefore there was always the need for a `-W` shortcut as well.
* `P` is a good choice because it is a file IO command in TECO-11,
  that does not make sense supporting.
  In Video TECO it toggles between display windows (ie. split screens)
  and I do not plan to support multiple windows in SciTECO.
* Added to the cheat sheet.

* This made sense to include both `W` and `V`, so we also included `D` and `K`.
  `^Q` is included since it converts between lines and glyphs.
* These are all single-letter commands, so they aren't complete parser states
  but callbacks to be referenced in teco_machine_main_transition_t.