my $text = get_text_from_db(..);
$text =~ s|\n|<br />|sg;

##</code><code>##

$text =~ s|\n\n|<br /><br />|sg;
$text =~ s|\n{2}|<br /><br />|sg;

##</code><code>##

$text =~ s|\n{2}(^<)|<br /><br />$1|sg;