Perl is not in itself a windowing client but it can drive libraries which display windows, as with Tk.

In the web context, if you use Javascript to create images in Netscape which automatically highlight on mouseover, Perl can modify that file on the fly to specify which images should be drawn. You would modify a template containing the Javascript on the fly.

If a gorgeous interface is the most important thing to you, Java or a DHTML interface with Javascript is the answer to the front end. Java or Perl can be used on the back end. Personally I find Swing too heavy and you can probably get everything you need for a web app through DHTML.