Get Win32::AdminMisc from http://www.roth.net/perl and then you can do this:

if (Win32::AdminMisc::UserCheckPassword($server, $user, $guess)) {
   print "$guess is correct password for $user";
} else {
   print "Bad Username or Password";
}
[download]

Update: To test whether they are part of a group, you will need to do this:

use Win32::NetAdmin;
$groupname = 'supercam';
if (GroupIsMember($server, $groupname, $user)) {
  print "user in group"; 
}  else  {
  print "user doesn't have permission...";
}
[download]

You should be able to combine both these to do what you want. In both the cases, if '$server' is empty, it defaults to the current machine.

Update 2: Hmm, I forgot about Win32::AuthenticateUser. Did it work? You could use that in conjunction with Win32::NetAdmin::GroupIsMember().

Check out Win32::AdminMisc anyway, because its got loads more there that will be useful if you're "forced" to use Windows =P

$code or die
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