JComboBox is a composite widget that contains a text Label or Entry, a
Button, and a popup Listbox. It performs the same sort of tasks that can be
accomplished by several other Composite widgets. Some such as BrowseEntry
and Optionmenu are part of the standard Tk distribution, and there are many
others available in CPAN.

JComboBox borrows features from the Java Swing component bearing the same
name, but falls short of being a true clone. Many of the methods and the
general look and feel should be familiar to java developers. JComboBox also
combines several features offered by many of the other "Combo Box"
implementations, and works in two modes: editable and readonly.

In readonly mode, JComboBox offers similar functionality to Optionmenu. It
is basically a labeled button that activates a popup list. An item from the
list is displayed on the Button when selected.

When editable, JComboBox somewhat resembles BrowseEntry. That is, the
widget is composed of an Entry widget with a Button to the right of it. As
in the editable mode, the Button activates a popup Listbox from which a
single item can be selected.

WWW: http://search.cpan.org/dist/Tk-JComboBox/