use strict;
use warnings;
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But I confess that I still don't trust -w on Windows (even though I now know it works perfectly well), because Windows ignores the first part of the shebang line.  To test this, you can do:

#!/usr/path/which/does/not/exist/perl
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and it'll still run Perl correctly.  Granted this isn't a reason to stop using -w, which still does work as I mentioned, but it did make me suspicious of the whole top line for quite a while.