cgi-callout form calling itself to get data ?

System

I have built an 'asset browser' cgi-callout in Perl that let's the user pick an asset from our asset work area, regardless of the workarea they are in. In it's initial form, the Perl code simply does a 'find' across the base Interwoven workarea in the file system to enumerate all of the directories and assets available. As that workarea gets populated, the list that returns is (1) slow to build and (2) huge {1800 assets currently available}!

What I want to do is present the user with a list of directories in one select list, and when they click on a directory in the asset structure, call my CGI again and have it fill a second selection list with the files found in the selected directory.

I figure that if I 'call myself' with a GET string containing the directory chosen, the population of the second list is easy.
I've looked a little bit at CGI.pm and CGI-Lite, and it seems like there are functions to cause the form to 'call itself' without losing form entries.

Has anyone tried this? I'm having a hard time figuring out what $cgi->function to call, and how the Interwoven cgi-wrapper might interfere/interact.

I'm also open to other ideas on how to have a cgi-callout make a secondary 'call out' to populate data based on user choices. I'm not clear if 'FormAPI' figures into this kind of thing (it seems more tied to the DCT).