node($m, promise { upto($m+1, $n) } );

##</code><code>##

#!/usr/bin/env perl

use strict;
use warnings;

sub promise (&) { $_[0] }

make_good_on_promise(promise { print @_ }, "Hello.\n");

sub make_good_on_promise {
    my ($promise_to_do, $whatever) = @_;

    $promise_to_do->($whatever);
}

##</code><code>##

$ pm_example.pl
Hello.
$