I'm not sure what you mean, but...for example you've created main window as in my prev post, with 2 buttons instead of input field (to make it simpler to explain)

...
$main->Button(-text => 'Test',
-command => \&Test)->pack(-side => 'left');
$main->Button(-text => 'Logging',
-command => \&LogOutput)->pack(-side => 'left');
...
MainLoop; #Here Main window ends
#And we declare our subs with own window for each
sub test{
my $TestWindow;
$TestWindow=$main->DialogBox(-title   => 'Test sub window',
                             -buttons => ["OK"]);
#We've created dialog box for test sub output
#Then folowing you testing code
...
Testing code =)
...
if($success){
$TestWindow->add("Label", -text => "Test passed!")->pack;
}
else {
$TestWindow->add("Label", -text => "Test Failed!")->pack;
  }
#Putting conditional output on our window
$TestWindow->Show(); # Poping it in front main window
#It is not separate window object, but dialog box produced  #by main o
+bject 
$InfoWindow->destroy; #Destroying it when OK pressed, and back to main
+ window
}
[download]

Same with logging sub..