Raise an error when option parameters are not delimited by comma
<p>I want option parser to raise an error when arguments passed to an option are not separated by the correct delimiter, comma. For example, in:</p>

<pre><code>script_name -p a b -s test
</code></pre>

<p><code>a</code> and <code>b</code> are separated not with a comma, but with a space. I want to throw an error for this.</p>

<p>Is there any sophisticated way of doing it?</p>