use Tk; use Time::Duration;
$start_time = time();
print "Start Time: $start_time\n";
$mw = MainWindow->new();
$timi = $mw->Label( -textvariable=>\$elapsed_time, -foreground=>'blue' )->pack;
$mw->Button( -text=>'Quit', -command=>sub{ exit } )->pack;
$mw->Button( -text=>'Update', -command=>sub{ print "New Time: $elapsed_time\n"; } )->pack;
sub update_time {$elapsed_time = concise(duration_exact(time() - $start_time)); $timi->update();}
$timi->repeat(50,\&update_time);
MainLoop;