Hi,

Try using https://metacpan.org/pod/distribution/Win32-GUI/GENERATED/Win32/GUI/Reference/Methods.pod#Hook

something like

$main->Hook( WM_DISPLAYCHANGE(), \&onDisplayChange );
sub onDisplayChange {
    my( $object, $wParam, $lParam, $type, $msgcode) = @_;
    print "Click handler called!\n";
}
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