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Perl 5.005 has inclusion of a new perl module called Threads. However the build of perl does not include this new feature even though the the OS is thread safe (glibc2.1). The bug is that you can still do man Thread and come up with the man page on perl threads, but you cannot use Thread; in a perl program. Either the man page should not be included or Perl should be built to allow for the use of this module. (Personally I'd go for building threads into perl)
We've looked at the threads issue, and building perl with -Duse_threads would require rebuilding every perl module we ship.
If guess you have alot of work cut out for you :-O. My suggestion would then be to remove the man page for perl Threads. Personally I think that it would be worth it to recompile every perl module you have. It could easily be done in a script to automate the build. The difficult part would be taking the perl modules and editing all the spec files.