I think the problem with perlthrtut and some other bits of the documentation (what there is of it), was mostly written for 5005threads and hasn't really caught up with ithreads yet.
That said. I'm not sure how the snippet you quote would have worked then either.
Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon