File A (login script):
...
$c = $query->cookie(-name=>'ID',
  -value=>( username=>$username,
            password=>$password )
          );			

print $query->redirect(-location=>$goodurl,-cookie=>$c);
exit 0;

File B (page viewer):

%cookies = fetch CGI::Cookie;
		
if(%cookies ne undef)
{
	if($cookies{'ID'} ne undef)
	{
		my %hash = $cookies{'ID'}->value;
		$username = $hash{'username'};
		$password = $hash{'password'};
	}
	else
	{
		# Cry, because this is where I keep ending up.
		# If I don't have check for the undef, 
		# $cookies{'ID'}->value actually kills the script...
	}
}