I suppose you'll need to remove just the COMPRESSED bit, and leave the rest of $attr as it is:

...
$attr &= ~COMPRESSED;
Win32::File::SetAttributes($path, $attr);
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BTW, for instructive purposes, you can visualize the bits with

print unpack("B*", pack("N", $attr)), "\n";
# or
printf "%032b\n", $attr;
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