I don't have an example handy, but Tk::ExecuteCommand has "advertised subwidgets", which means you can access the various components separately, and change their appearance. So you could make the stdout textbox, nearly invisible. For that matter, you could run it with the window "withdrawn", to make it totally invisible. You also could setup custom key bindings, to call the same "Quit" subroutine, as the Execute/Stop button has. Read perldoc Tk::ExecuteCommand and look for the "ADVERTISED SUBWIDGETS" section. You possibly could do something like:

my $rotext = $ec->Subwidget(ROText);
$rotext->configure(-height => 0);
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and you could add key bindings, like

$text->bind('<Control-r>',sub{$ec->kill_command });
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Of course, this only works from X, if you want it to work from the command line, try POE; maybe the POE Cookbook has some examples.