A reasonably portable way to do this is using the sysconf(3C) function. Unfortunately you can only call it from C.

If you use the amazing Inline module, a function to get the number of CPUs is as easy as 

use Inline C => qq{
#include <unistd.h>
long nprocs() { return sysconf(_SC_NPROCESSORS_CONF); }
};

my $num_cpus = nprocs();

This get the number of CPUs configured; replace "CONF" with "ONLN" to get the number of CPUs on line.

UPDATE

The standard module POSIX defines POSIX::sysconf. Unfortunately it doesn't appear to define the constants _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN, so it doesn't solve your problem.

In reply to Re: Multiprocessor (SMP) system detection by ariels
in thread Multiprocessor (SMP) system detection by PetaMem

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