Hi Hidetoshi,

I understand your need and as I asked for help, I have to help you back
:)

So I applied the patch to tk.rb :
==============================
...
set __initial_state_of_rubytk__ 1
trace add variable __initial_state_of_rubytk__ unset
__startup_rbtk_mainloop__
update
EOS

        begin
          begin
            #TclTkLib.mainloop_abort_on_exception = false
...
and
...
      }

      until INTERP_THREAD[:interp]
        #Thread.pass
   INTERP_THREAD.run
      end
      # INTERP_THREAD.run
      raise INTERP_THREAD[:interp] if INTERP_THREAD[:interp].kind_of?
Exception
...
==============================

Running the small script gives the same problem ; here is the end of the
debug output showing an exception :
==============================
tcltklib: destroy root widget
tcltklib: check `finalize-hook-proc'
tcltklib: check `foreach' & `after'
tcltklib: cancel after callbacks
tcltklib: finish ip_finalize
Exception `TypeError' at /usr/lib/ruby/1.9.1/tk.rb:1283 - exception
class/object expected
tcltklib: eventloop_ensure: current-thread : 8802278
tcltklib: eventloop_ensure: eventloop-thread : 8802278
tcltklib: eventloop-ensure: new eventloop-thread -> 4
tcltklib: finish current eventloop 8802278
tcltklib: ip is deleted
tcltklib: ip is deleted
tcltklib: ip is deleted
tcltklib: delete deleted IP
tcltklib: free Tcl Interp 881a678
tcltklib: complete freeing Tcl Interp
==============================

But the weird thing is that sometimes it runs OK ! (once every 6 ou 7
times) ; I just run the same command again and again...

Hope this will help !

Best regards
Stéphane