The answer is because as stated in the original post, the commented line that sets the permissions works.

If your perl script has sufficient authority to modify the permissions, then it has sufficient authority to use (I|X)cacls.exe to modify those permissions.

I just can't figure out how to modify the existing permissions.

Which is why I suggested you use (I|X)cacls to do the job. Because they are easier to figure out. And they are less likely to screw up existing permissions as you add new ones.

I'm beginning to think it just isn't possible and that is certainly disappointing.

It is possible. It's just quite hard to get right. In general, when modifying bitmapped values, the process is:

$toAdd = (BIT1 | BIT4 | BIT7);
$old = getOld( X );
$new = $old | $toAdd;
put( X, $new );
[download]

I really do appreciate your assistance but in all honesty I am not getting any useful information. I need to do this in Perl. You stated "If your perl script has sufficient authority to modify the permissions, then it has sufficient authority to use (I|X)cacls.exe to modify those permissions." While that may be true, it doesn't help at all. The Perl script has sufficient permission but as stated earlier, IIS6 won't let this happen. So, back to the exact same question I started with. How do I accomplish this in Perl?

but as stated earlier, IIS6 won't let this happen.

How can IIS stop it? If your Perl script has the authority to do it; then calling system to use a utility to do will also work unless there is some mysterious mechanism at work.

Beside which, I already told you how to do it. You have to bit-wise OR the new permissions with the existing ones, before (re-)setting them.

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In the absence of evidence, opinion is indistinguishable from prejudice.

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Is there a read permission command? With many other things, you need to read the existing, apply your changes, and write them back out. Is this one of those things?