To get rid of lines containing nothing at all you could do something like this:

#!/usr/bin/perl -w

use strict;

while (<>) {
    next if (/^\n/);
    print;
}
[download]

where the regex matches lines which start with a newline chartacter. If you also wanted to ignore lines which contained only spaces you could try replacing the regex line with

next if (/^\s*$/);
[download]