Ahem.

Perl = Language definition
perl = Implmenentation of that language
PERL = ???
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There's no such thing as 'PERL', unless it exists elsewhere in the English language.

Now for your question: Before JavaScript existed, everyone did everything with server-side programs. Perl has fit this domain well. However, there are things on the client side (which is where JavaScript lives) that can make the process more efficent. For instance, say you have a form that has certain required fields. Before JavaScript, if any of these fields weren't filled out, the client would submit the form and the server would return an error saying the form wasn't completely filled out. With JavaScript, we can stop the user from submitting an invalid form in the first place, thus saving bandwidth and the time it takes for a server to execute the program to parse the form input.

However, JavaScript can be shut off by the client. If the programmer in our example above said "JavaScript is doing the form validation, so there is no need to do it on the server side", then we could have a problem. A client that shuts off JavaScript would still be able to submit the form, and the server program would dutifully parse it. Thus, while JavaScript is often a useful tool, your Perl programs should be written to assume that it is shut off.

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I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated