The code is doing exaactly what you instructed to to do: with while($window[0]) you say "during the time it is defined my first found window.." ie is an infinite loop.

The condition is checked continuosly and while it is true the program is expected to print your calculator window is open sentences. It is expected but it does not do; why? because the buffer it is not full. Generally speking command line programs are line buffered. Try to add a newline at the end of your sentence and see what happens. You can also force a non buffered output using $| and assigning somenthi true to it; the idiom is $|++; see perlvar

For the buffer implication see the Suffering from buffering? milestone article.

For Win32::GuiTest at the end of the module documentation is linked the site of the author which contains good winguitest tutorials

L*