my ($field1, $field2, $field3) = (undef, undef, undef);
my $sth = $dbh->prepare('select * from table');
$sth->execute;
if ($sth->rows > 0) {
    $sth->bind_columns(\($field1, $field2, $field3));
    $sth->fetch;
}
$sth->finish;
for ($field1, $field2, $field3) { $_ ||= '' }