Thanks Zaxo, castaway and liz for replying. After more investigation, now I clearly believe that it is detach() now broken. The version I used is Win32, but the bug could well be across all platforms. Although as liz pointed out, the threading implementation is platform specific, I believe, most likely what broken is the common wrapper on top of the threading.

Theoritically, there was no need for detach() in my code. I added them against my own will, as it was a must under 5.8.1 thread. Under 5.8.1, there was a huge memory leak without detach(), making it even worse, Perl didn't check null pointer returned from malloc, and after a while, once the memory leak is big enough, and the program can no longer allocate memory, the script just crashes.

I tried to remove those detach(), and ran my script again, it seems fine, and no longer crashes like 5.8.1. But as I pointed out, now detach() core dumps.

This is really a warning sign, and I am really concerned about the quality of, not just a particular release, but their development and verification process. To be frank, it is a big surprise to see that, they didn't carefully test some basic cases in the area, which they applied some big fixes.

I am not worried about couple of bugs, but I can become really concerned if there are evidences showing that the way they control the quality of releases is flawed, and their verification (testing) process is flawed.

We cannot control the quality of other people's work, but at least I can report the problem, and help them a little bit.