The code you sent works for me. I don't know what's going on.
$MainWin = new Win32::GUI::Window(
-name => "MainWin",
-text => "Main Window",
-height => 400,
-width => 450,
-left => 200,
-top => 100,
-font => $Font,
-menu => $Menu,
-resizable => 0,
);
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