One point to make on the above answer. From what I can tell, you need 2 perl scripts. One that generates the form on the fly, pulling default values from your test.cfg file, and one that is the action of your form, that populates the test.cfg, and or does something else with the data as well. You could probably do it all in a single script, by checking to see how your script was called, ie with or without params, but it might be less confusing for you to use two.

The key is to generate your form from a script that can look at your config file. HTML cannot look at your config file, nor can javascript.