perl -le 'print $^O'

##</code><code>##

package System::CPU;
use strict;

sub nr_cpus {
  $^O eq 'linux'   and return nr_cpus_linux();
  $^O eq 'solaris' and return nr_cpus_solaris();
  $^O eq 'palm'    and return 1;
  1; # default if we don't know any better
}

sub nr_cpus_linux {
  # your code here
}

sub nr_cpus_solaris {
  require Solaris::Funky::Stuff;
  Solaris::Funky::Stuff->import();
}

1;

##</code><code>##

  my $cpus = System::CPU::nr_cpus;