Basically you will need a frontend made with Mojolicious (full featured perl web framework; great documentation) or Dancer2 (probably easier to get started) to fetch users parameters. Then you can use Template::Toolkit (or something similar in CPAN like Text::Xslate ) to customize users pages.

Then you ship these customized templates into an Apache (external?) webserver, automate the Apache configuration to load this new content, eventually automate the DNS population entry for this new website.

In the front end you can implement a queue manager to put on the queue all the steps, so you can render a page telling the user that the work is in progress.

Is not exactly my field and I never done something similar, but I'd proceed this way. Sounds fun :)

I have some link about learning Perl in my bibliotheca

Share here your doubts in a clear way, with code examples and you will get for sure better support.

L*