CLIP file size limit

#1
How much data can be redirected to CLIP: ? One of my batch files hung,
apparently because I tried to write too much to it, though it might have
hung when executing %@LINES[CLIP:]. This implies that new internal
variables, _CLIPSIZE (characters) and _CLIPLINES would be very useful, along
with _CLIPTEXT (1 if clipboard contains text, 0 otherwise). A command to
clear the clipboard would likewise be useful.
--
Steve