use strict;
my $OS_TYPE = $^O eq 'MSWin32' ? 'win' :
              ($^O eq 'nonstop_kernel' ? 'nsk' : 'unix');
sub XPlat::win_fn  { print "windows version of function\n" }
sub XPlat::nsk_fn  { print "nsk version of function\n"     }
sub XPlat::unix_fn { print "unix version of function\n"    }
sub xplatform_fn   { return &{$XPlat::{$OS_TYPE."_fn"}} }
xplatform_fn();