Hmmm, that is so interesting. I've been banging my head on a typo from the Camel?
After reading your post, I went back and compared

select((select(TO_CHILD), $| = 1))[0]);
[download]

between what I wrote and the book. That is exactly as it appears in the 3rd edition of the Camel under Bidirectional Communication on page 432.

Thank you for the $childnum suggestion, but where am I supposed to get that value from? The $pid results in a negative number for me. Searching for $childnum reveals only two nodes. And a search on PerlDoc turns up nothing :(