Hi Zecho,
You can prevent both empty and whitespace names by matching one word character:

my $user = ( $q->param('user') =~ /\w/ ) ? $q->param('user') : "Anonym
+ous";
[download]

but it would also be well to apply escapeHTML to $message and s/[^\x00-\x1f\x7f]//g for ($user,$message); as well. That will knock off unprintable nasties.

A minor point, you probably should use '<br/>' for xhtml correctness.

Update: changed break tag comment per blackmateria's reply, Thanks!

After Compline,
Zaxo