I am totally new to perl

You might find perlintro helpful in getting started with the basics.

In addition to Corion's advice, if you want to randomize your parameters, you could use rand or Data::Random.

If you want more specific advice, post a small sample of the output VHDL code you want, along with some example parameter types.

Update: it's always a good idea to search CPAN to see if you can leverage work done by others. In this case, however, it looks like there are only VHDL parsers, not generators.