Thanks for the hint, that was all I need. I knew their is some function to get all the active windows and checking those windows does the job. Works very nice. Below my code for reference

# Used to focus windows on the top
use Win32::GuiTest qw(FindWindowLike GetWindowText
    SetForegroundWindow SendKeys);

while ($found == 0)
{
 $found = FindWindowLike(0, 'Engineering Toolkit', "");
 sleep (4); 
 print "Application is still starting Wait .........\n";
}
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