foreach $Author2 ( @author_order ) { 
     $auth  = $author_books{ $Author2 };
    my $books = $auth->{order}; 
    push @body, "<tr><td rowspan="${\scalar, @$books}"$Author2</td>\n";
    my $line = 0;
    foreach my $book ( @$books ) { 
        push @body, '<tr><td></td>' if ++$line;
        push @body
           , ( "<td>$book</td><td>"
             . join( "<br/>\n", @{ $auth->{books}{ $book } } )
             . "</td><tr>\n"
             );
    }
} 
##</code><code>##

<tr><td rowspan="$"
        (Missing operator before $?)
String found where operator expected at rough.pl line 43, near "}"$Author2</td>\n""
        (Missing operator before "$Author2</td>\n"?)
syntax error at rough.pl line 43, near ""<tr><td rowspan="$"