The activate method will set the listbox item at index index to the active element. This allows you to access this item later using the "active" index. Figure 7.4 shows two windows with active elements underlined. Each listbox also has the black highlight rectangle around it, which indicates it has the keyboard focus (the active element isn't seen as marked unless the listbox has focus).
# The first window activates the item "four" $lb->activate(3); $lb->focus(); # The second window activates the item "three" $lb2->activate(2); $lb2->focus();