This file is used to provide persistent variables of a spell to another spell.
For example here's EXPORTS file from "xorg-server" spell:
XORG_SERVER_OPTS
which is used later in DEPENDS of "x11vnc" spell:
persistent_read xorg-server XORG_SERVER_OPTS XORG_SERVER_OPTS &&
if list_find "$XORG_SERVER_OPTS" "--enable-record"; then
config_query_option X11VNC_OPTS \
"Enable xrecord extension support?" y \
"--with-xrecord" \
"--without-xrecord"
fiNote: since the variables are read from within a spell's tablet, don't forget to add a REPAIR^all^EXPORTS file if needed.