So, likely, no, you are not sending the same data as your Java program.

The LWP::UserAgent (resp. HTTP::Request) modules (and objects) have methods to print themselves as strings. Use these to find out whether you are initializing them wrongly or whether you are not sending all data.

Also consider looking at WWW::Mechanize or at least HTML::Form to make form submission easier, at least if you have a HTML form that you're trying to automate.