HTML5, of course, is merely a means of expression.   And, “the web page” that you are describing is merely a user interface to a much larger and more complex “back-end” system.

The back-end system that you are describing might have been, in earlier days, described as “a batch-processing system.”   Or maybe, “an application server.”   Be very mindful that a suitable system probably already exists, and that it most certainly will also have a web-based UI available.

You are definitely in the “requirements definition” stage, having not yet even begun the due-diligence that needs to happen to consider all of the relevant implementation options that you or this project might have.   You are, therefore, a long way (IMHO....) from being ready to consider questions of Perl, mod_perl, and/or HTML5 ...

In fact, it is rather profoundly important at this stage to bear in mind that “this is not the Starship Enterprise.”   No matter where you may happen to be going, you are not “boldly going where no man has gone before.”