This small low-level module only has one purpose: pass a file
descriptor to another process, using a (streaming) unix domain socket
(on POSIX systems) or any (streaming) socket (on WIN32 systems).  The
ability to pass file descriptors on windows is currently the unique
selling point of this module. Have I mentioned that it is really
small, too?

WWW: http://search.cpan.org/dist/IO-FDPass/