You're very close. To make your first example work, you need to just add a dollar sign in front of info when you dereference:

while($info = $sth->fetchrow_hashref) {
    @case = keys %{ $info };
    print @case; 
}
[download]

Once you do this, you'll see that your second example is basically the same as the first, except it iterates thought the hash instead of dumping the keys all at once.

HTH.