Threads
Perl 5.005 also includes the first release of a native multithreading capability, which is distributed with Perl as a set of modules. Since this is an initial release, the threads modules are considered to be beta software and aren't automatically compiled in with Perl. Therefore, the decision to use the threads feature has to be made during installation, so it can be included in the build of Perl. Or you might want to build a separate version of Perl for testing purposes.
describes the individual Thread modules. For information on what threads are and how you might use them, see the article "Threads" in the Summer 1998 issue of The Perl Journal. There is also an explanation of threads in the tutorial Developing with Perl Modules from Anonymous's Perl Resource Kit, Win32 version.