Variable names can contain dashes?<p>Then how do you know what this means:<p><pre><code>    users=users-churn-rate*time
</code></pre>
oh, i see ... they are prefixed with $. so it&#x27;s:<p><pre><code>    $users=$users-$churn-rate*$time
</code></pre>
Hm... still a bit confusing. But ok. It can be avoided by avoiding dashes in variable names.