Use a Package Command

By the end of this chapter, you will have transformed a selected region through rot13-region, preserved surrounding Unicode text and undone the whole change with one ordinary undo step. The verified rur.rot13 release must be enabled.

Create or open a disposable UTF-8 note containing:

outside|Abc λ界 é🙂|tail

Select only Abc λ界 é🙂 using the region controls from Move and Retain Text. In either profile you can use Alt-x goto-character, enter 9, invoke set-mark, then use goto-character and enter 18. Those positions count Unicode scalars from one, not UTF-8 bytes. The selection ends before the second |.

Invoke rot13-region through Alt-x. The note becomes:

outside|Nop λ界 é🙂|tail

ASCII letters in the region change. The prefix, suffix, newline and other Unicode scalars remain exactly as they were. Invoke undo once to restore the original region, then redo once to restore the transform. Save with Ctrl-X Ctrl-S and inspect the file after leaving the editor.

Invoke deactivate-mark, then try rot13-region again. Without a selection the command is unavailable or refused without mutation. It cannot invent a target or bypass the ordinary checked transaction and history owners. Package execution has bounded time, memory and effects; a worker error is not a successful edit. Use package-doctor and the feedback history to inspect a failed operation.

A command can disappear when you disable its package or replace its generation. That visibility follows the confirmed lifecycle, independently of saved source files and catalog display names. Trusted personal configuration remains a separate authority; packages do not inherit its host access.

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