use Data::Dumper;

my $N = Value->new(23);

warn Dumper($N * 2);
warn Dumper($N*= 2);

my $test;
$test->{obj} = $N;

warn Dumper($N * 2);
warn Dumper($N*= 2);

package Value;

use overload ('*=' => 'mulSet');
use overload ('*' => 'mul');

sub new {
	my ($class, $value) = (shift, @_);
	$class = ref($class) || $class;
	my $self = {value => $value};
	return bless $self, $class;
}

sub mul {
	my ($self, $num) = @_;
	return $self->new($self->{value} * $num);
}

sub mulSet {
	my ($self, $num) = @_;
	$self->{value}*= $num;
	return $self;	
}

##</code><code>##

$VAR1 = bless( {
                 'value' => 46
               }, 'Value' );
$VAR1 = bless( {
                 'value' => 46
               }, 'Value' );
$VAR1 = bless( {
                 'value' => 92
               }, 'Value' );
Operation "=": no method found, argument in overloaded package Value
at /bla/bla/bla/test/Value.pl line 12.

##</code><code>##

$test->{obj} = $N;
use overload ('*=' => 'mulSet');

##</code><code>##

return $self;