There is no specific problem of this type with either threads, perl 5.10 nor AS Perl 5.10. The following creates and joins 1000 threads (and it'll do 10,000 quite happily except that it will push my machine into swapping):

perl -Mthreads 
-E"@t= map async( sub{say threads->tid;sleep10;}),1..1000;$_->join for
+ @t"
[download]

(Any problem listed on the AS site 5 years ago has long since been fixed. It was probably an entirely different type of threading all together that long ago.

The problem is almost certainly what you are doing inside the threads. to get a workaraound you need to post the code, or a cut down version that demonstrates your problem.