# The first one is wrong. It adds a reference to an subroutine named for the return value of $ship->move (or \&1) 
# because print returns 1 when it is successful.
$app->add_move_handler ( \&{$ship->move} ); 

$app->add_move_handler ( sub { $ship->move( @_ ) } );

##</code><code>##

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Deparse = 1;

use Mob;

my $ship = Mob->new();

my $first = \&{$ship->move};
print "first: ", Dumper( $first );

my $second = sub { $ship->move( @_ ) };
print "second: ", Dumper( $second );

# &$first(); # Uncomment to see the error 'Undefined subroutine &main::1 called at ./test.pl line 17.'

&$second( 1, 2 );