I think that you may be approaching this from the wrong direction. I know that when I've done this kind of thing with Win32::OLE and the ADSI interface I modify the group to add the user, you appear to be trying to modify the user to add the group.

Just a thought.

Updated:

I managed to check this out this morning. Yes, one modifies group membership in the group itself. How this maps to use from Net::LDAP, I'm not sure. Maybe:

my $result = $ldapConnection->modify ($groupDn,
        add => $userDn, );
[download]