Hi,

Those don't look to be actual constants in the perl sense(empty prototype)/use constant

$ perl -MO=Deparse -MWin32::Sound -e " print Win32::Sound::SND_NODEFAU
+LT & Win32::Sound::SND_ASYNC "
use Win32::Sound;
print Win32::Sound::SND_NODEFAULT(&Win32::Sound::SND_ASYNC);
-e syntax OK
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Its one of the reasons I tend to always use () for anything called constants in the docs

$ perl  -MWin32::Sound -e " print Win32::Sound::SND_NODEFAULT() & Win3
+2::Sound::SND_ASYNC() "
0
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update: after looking at the source, I see they're also autoloaded using some old ExtUtils::Constant code ... and there is a warning about that in https://metacpan.org/pod/Exporter#AUTOLOADed-Constants

You might wish to report this bug to rt://Win32-Sound, all that autoload stuff for 20 constants seems like it belongs in the past :)