Or if you want to remove blank lines:

s/\n{2,}/\n/g;
[download]

If you want to clump everything into a single line (maybe for reformatting it yourself, see Text::Wrap or my Nicely format a list or a string snippet):

s/\s+/ /g;
[download]

If you want to cut it to the first 5 non-empty lines:

$text=join("\n",(split(/\n+/,$text))[0..4])
[download]

I don't think there is an HTML attribute to restrict the number of lines in a TEXTAREA.

--ZZamboni