Function: completion-in-region-mode

Transient minor mode used during `completion-in-region'.
With a prefix argument ARG, enable the modemode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
the mode if ARG is omitted or nil.

(fn &optional ARG)

Variable: completion-in-region-mode

Non-nil if Completion-In-Region mode is enabled.
See the command `completion-in-region-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `completion-in-region-mode'.