my $book = MyPackage->new( # stuff );

##</code><code>##

my $book = MyPackage->new( # stuff );
print CGI::redirect(-uri=>"login.cgi?msg=$book->{error_msg}")
   unless $book->{login_successful};

##</code><code>##

print CGI::redirect(-uri=>"login.cgi?msg=$book->{no_access}")
  if $book->{user_access_level} < $book->{required_access_level};