In 8.4.10, a change was introduced in menu.tcl, which
made Unix popup menus stay open when the mouse button
was released over a non-active item or the menu border.
This is a feature change that breaks the previous Unix
popup menu behaviour. Refer to menu.n which states:
"When a button is released over a menu, the active
entry (if any) is invoked.
The menu also unposts unless it is a torn-off menu."
Rather, the previous behaviour should be retained.