5.8.0 the interpeter threads became available from perl level through
the threads and threads::shared modules (in Perl 5.6 ithreads are
available only internally and to XS extension builders, and used
-by the Win32 port for emulating fork()).
+by the Win32 port for emulating fork()). As of Perl 5.8.0, ithreads has
+become the standard threading model for Perl.
If you really want the older support for threads described below,
it is enabled with: