Hi,
  I haven't used threads before, but your problem is either is_joinable is not a function of threads. Or your version of threads does not include is_joinable. So I recommend that you upgrade your version of "threads.pm" to the latest one avilable at cpan. Make sure you do a proper install using perl -MCPAN -e shell; orby downloading and installing the zip, don't just copy and paste threads.pm.

Lyle Hopkins