I suggest that you start the page in a browser while running a debugger such as FireBug.   This will allow you to do two very useful things:

1. You can set breakpoints in the JavaScript code, to see what it is doing and where/when it is being called.
2. When the page finally submits something to the host, you can see the actual GET/POST that it sent.   Never Assume.™

You don’t say whether the JavaScript code is known-good, so let’s assume, until demonstrated otherwise, that it is the actual source of the bug.   Let’s assume that the real problem is that the JavaScript either isn’t passing mysample, or that its value is empty.   Exercise the code and use FireBug to find the actual POST.   If you can see the correct value being passed, only then do you know (but now, you know), that the error is in the Perl software.