Availability:built-in
attach_packspack. The default for this search path is given below. See
file_search_path/2
for the app_data search path.
user:file_search_path(pack, app_data(pack)).
The default path may be overruled with the environment variable
SWIPL_PACK_PATH. This variable must contain a list of
directories separated by the OS-specific path_sep.
The predicate attach_packs/0 is called on startup of SWI-Prolog.