Thank you for your reply.

The objectGUID of an Active Directory user (as well as some other attributes like userCert(ificate), password, ...) is defined in the Schema as Octett which may contain non printable chars (e.g. A+§R9Ð?@½!í+Å?ÐR).

If I look it up in the schema with ADSI, I don't know yet on how to read the format of an attribute. With the following code I can access the schema, but only know the properties of mandatory and optional attributes.

# $adsPath is the path to a user object
my $object = Win32::OLE->GetObject($adsPath) or die "...";

my $schemaObj = Win32::OLE->GetObject($object->{Schema}) or die "...";

my @mandatoryAttributes = $schemaObj->{MandatoryProperties};
my @optionalAttributes  = $schemaObj->{OptionalProperties};
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If I could get the format for an attribute, I could as well find out if it is binary or not