Buffer size doesn't seem to be it, since I can turn on autoflush in the parent and see writes as they happen in the child. Also buffer size doesn't explain the child not seeing the parent close the pipe, and the child not seeing the parent exit.

That node pipe fork win32 is good reading but the poster states "If I add a 'close($parent);' after 'print $parent "exit now\r\n\r";' it works."- which is what I have in the one-liner, closing the parent's end of the pipe after I print to it.