Tk::JComboBox is poor substitute, Tcl/Tk allows similar widgets *yet* it allows native drop-down box!

MListbox - look at http://mini.net/tcl/6784

Tk::DynaTabFrame - BLT's tabs are MUCH more attractive, yet more powerful, see http://vkonovalov.ru/cgi-bin/perl-tcltk-wiki.cgi/40

As for your own pure-perl widgets -- sorry, no coffee.
perl/Tk's megawidgets are done with Tix, and I even implemented compatibility stuff in Tcl::Tk which worked, but I never released this because I lost interest in this.