Perl 6 Deep Dive

Factory methods

Let us start with a simple program that creates a promise with a code block that prints something and exits. The Promise.start method creates a block and returns a promise. Notice that the returned value is a promise, not a thread. To wait until the code block of the promise is done, use the await function:

my $promise = Promise.start({    say 'I am a promise';});await $promise;

The program waits until the message is printed by the code block and exits:

I am a promise

In the preceding example, the start routine is called as a method of the Promise class. Alternatively, a promise can be created by a self-standing start function:

my $promise = start {    say 'I am a promise';};await $promise;

Notice that there are no parentheses ...