jka-compr-mode-alist-additions--internal

jka-compr-mode-alist-additions--internal is a variable defined in `jka-cmpr-hook.el'.
Its value is

(("\\.tgz\\'" . tar-mode)
 ("\\.tbz2?\\'" . tar-mode)
 ("\\.txz\\'" . tar-mode))

Documentation:
Stored value of `jka-compr-mode-alist-additions'.
If Auto Compression mode is enabled, this is the value of
`jka-compr-mode-alist-additions' when `jka-compr-install' was last called.
Otherwise, it is nil.