use strict;
use warnings;

use Win32::API;

my $NOT_RESPONDING = 'Your App (Not Responding)';

use constant  GW_CHILD    => 5;
use constant  GW_HWNDNEXT => 2;

Win32::API->Import('user32', 'HWND GetDesktopWindow()');
Win32::API->Import('user32', 'HWND GetWindow(HWND hWnd, UINT uCmd)');
Win32::API->Import('user32', 'GetWindowText', 'LPi', 'i');


my $hwnd = GetDesktopWindow();

$hwnd = GetWindow($hwnd, GW_CHILD);

while ($hwnd)  {
    $hwnd = GetWindow($hwnd, GW_HWNDNEXT);

    my $title = 'x' x 256;
    GetWindowText($hwnd, $title, length($title) - 1);

    if ($title =~ /\Q$NOT_RESPONDING/) {
        print "Detected: $NOT_RESPONDING\n";
    }
}