my $effect = Effect->new(
    [ salary    => 1.02, '*' ],
    [ frobnitz  => 1.5, '+'  ],
);
$_->apply_effect( $effect ) for @employees;

##</code><code>##

my $effect = Effect->new;
$effect->salary *= 1.02;
$effect->frobnitz += 1.5;

$_->apply_effect( $effect ) for @employees;

##</code><code>##

$effect->salary = $effect->frobnitz + 1.5;