I added the reference to Win32API::Registry and updated the connect call:

my $remKey= $Registry->Connect( $pc, $regKeyName,
  { Access=>Win32::TieRegistry::KEY_READ() } )
  or Carp::croak("!! Couldn't connect to $pc or can't open reg key ($r
+egKeyName).\n".
    "!! - Is File and Printer Sharing enabled?\n".
    Win32API::Registry::regLastError(). "\n");
[download]

Please forgive the package names in the code. This is actually part of my first Perl program (tm), and I applied a package name to my code, so I've been fully qualifying variables from config files, etc.)

I'm now getting a more explicable error message, Access is denied. I tried using regedit to connect remotely to the Vista box, and was denied access, so this appears to be the root cause, and gives me a quick reality check.

I will reply once I figure out how to fix the permission issue.

--- Update 1/23, 13:26 ---

On the Vista box, I started the Remote Registry Service and set it to Automatic. Now I can connect to the Vista registry remotely, using regedit; however...

I only have access to HKEY_USERS/ and its subkeys. Frustratingly, HKEY_LOCAL_MACHINE is visible, but presents the following error when I try to access it, Cannot open HKEY_LOCAL_MACHINE: Error while opening key. I've tried tweaking various local security policy settings. I guess this is more of a Windows question at this point. I will try pursuing it further on a Windows forum.