can i both write & read a pipe?

[Asko Kauppi <asko.kauppi@...>]

It seems 'popen' is only read, or write, but not both.
What I'm trying to do is like:

	echo blahblahblah | osascript | (catch output)

That is, Lua would be both feeding in _and_ reading the output of the 
'osascript' command (which runs AppleScript on OS X).

-ak