You have to be very careful when building html like this, otherwise you'll keep running into the problems you are posting about now. Separating your code from the HTML using a templating module is a great start, using a modern framework (such as Mojolicious::Lite) to do the heavy lifting for you will save you a lot of time once you get used to it.

Again, this is likely a syntax error far more upwards in the source code.

Reduce your code and/or restore the original version from backup.

As a first step, I recommend changing all double quotes to be seen by Perl to a qq construct:

$string .= qq{<a href=\"/cgi-bin/recordz.cgi?ng=$lang&amp;page=main&se
+ssion=$session_id&amp;min_index_our_selection=$min_index&amp;max_inde
+x_our_selection=$max_index&amp;country_swiss=$country_swiss&amp;count
+ry_france=$country_france&amp;with_lang_french=$with_lang_french&with
+_lang_german=$with_lang_german&amp;with_lang_italian=$with_lang_itali
+an&amp;with_lang_english=$with_lang_english\" ><-$j-></a>&#160;&nbsp;
+};
[download]

That way, if you have an unescaped double quote within that string, it will do no harm to the Perl code.

In the long run, you might want to use a templating system (for example Template::Toolkit or the one from Mojolicious) instead of having HTML strings within your source code.