$data = qw( aaa bbb ccc );
$fields = scalar @data;
$data_fields = "";
map $data_fields .= '"' . $_ . '"', @data;
$format = "format STDOUT = \n"
        . "@<<< " x $fields . "\n"
        . $data_fields . "\n";
        . ".\n";
eval $format;
write;