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otherwise it is an equivalent to:

    my $d = deferred();
    $d->resolve($arg);
    $d->promise;

=item C<is_promise($arg)>

Returns true if the argument is a promise (object with method C<then>).

=back

=head1 SEE ALSO

=over 4 

=item L<AnyEvent>

To use this module it is necessary to have basic understanding of L<AnyEvent> event loop.

=item L<Promises>

Although L<AnyEvent::Promises> is similar to L<Promises> 
(and you can use its more thorough documentation to understand the concept of promises)
there are important differences. 

AnyEvent::Promises does not work without running event loop 
based on L<AnyEvent>. All C<$on_fulfilled>, C<$on_rejected> handlers 
(arguments of C<then> method) are run in "next tick" of event loop
as is required in 2.2.4 of the promises spec L<< http://promises-aplus.github.io/promises-spec/#point-39 >>.

There is also a crucial difference in C<$on_reject> handler behaviour
(exception handling). Look at

    my $d = deferred();
    $d->reject($reason);
    my $p = $d->promise->then(
        sub { },
        sub {
            return @_;
        }
    );

    $p->then(
        sub {
            warn "Code here is called when using AnyEvent::Promises";
        },
        sub {
            warn "Code here is called when using Promises";
        }
    );

With C<Promises> the C<$p> promise is finally rejected with C<$reason>,
while with C<AnyEvent::Promises> the C<$promise> is finally fulfilled
with C<$reason>, because the exception was handled (the handler did not
throw an exception).

=item L<https://github.com/kriskowal/q/wiki/API-Reference>

Here I shamelessly copied the ideas from.

=back

=head1 AUTHOR

Roman Daniel <roman.daniel@davosro.cz>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2014 by Roman Daniel.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut