Pthread::GetThreadId is FreeBSD specific Perl module
providing single non-portable function getthreadid_np()
that returns kernel level POSIX thread id as integer value.

It may be useful for Perl code running as hook/callback functions
in embedded threaded Perl environment when code has no direct control
on thread creation. For example, rlm_perl module of FreeRADIUS
that may use multiple embedded Perl instances.