use strict;
sub win_fn  { print "windows version of function\n" }
sub nsk_fn  { print "nsk version of function\n"     }
sub unix_fn { print "unix version of function\n"    }
sub xplatform_fn {
    if ($^O eq 'MSWin32') {
        return win_fn();
    } elsif ($^O eq 'nonstop_kernel') {
        return nsk_fn();
    } else {
        return unix_fn();
    }
}
xplatform_fn();

##</code><code>##

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

##</code><code>##

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();