toplevel

Tcl/Tk

#!/usr/local/bin/wish4.2

proc make_win {} {
	catch {destroy .win}
	toplevel .win
	button .win.b -text "Window Dismiss" -command {destroy .win}
	pack .win.b
}

button .b -text "make Window" -command {make_win}
pack .b -fill x

ruby/Tk

#!/usr/local/bin/ruby

require "tk"

def make_win
  begin
	$win.destroy
  rescue
  end
  $win = TkToplevel.new
  TkButton.new($win) {
	text 'Window Dismiss'
	command "$win.destroy"
	pack
  }
end

TkButton.new {
  text 'make Window'
  command 'make_win'
  pack('fill' => 'x')
}

Tk.mainloop