make shit up? No the reference was CPAN http://search.cpan.org/~nwclark/perl-5.8.8/ext/threads/threads.pm - Look neither of us obviously is responsible for the accuracy of documentation on this subject. But the fact remains that threads and forks existed before Perl and the intended functionality is entirely independent of Perl or anything released in Perl whenever. All you're doing is proving that even if the implementation is reliable, it still needs better documentation. And some article somewhen doesn't cut it - either Perldoc needs updating to describe the restrictions clearly, or the implementation needs to be improved so that the warning in the docs can be removed. Surely there is no way out other than these two options although I am open to suggestions.