my $employee = Employee->new( salary => 50_000 );
my $effect = Effect->new;
$effect->set( salary => 1.02, '*' ); # A 2% raise
$effect->set( frobnitz => 1.5, '+' ); # The frobnitz is up
$employee->apply_effect( $effect );

##</code><code>##

$employee->salary(  $employee->salary * 1.02  );