I too, usually use Tk. There is a simple GU code generator for it called vptk that I also use. Also, I created a menu builder "super widget".

Also, I've heard good things about the WxWidgets GTK toolkit and the Glade GUI builder for it (there are modules for generating Perl code from Glade description files). Not yet tried it.

Update: I meant GTK, not WxWidgets.