$pad = ' ' x 80;  ## make the length the same as your max expected

$c = "test test test";
$fmt = "A4 x1 A4 x1 A4 x1 A4";
@c = unpack($fmt, "$c$pad");
print join ("*",@c), "\n";

$d = "test test test ";
$fmt = "A4 x1 A4 x1 A4 x1 A4";
@d = unpack($fmt, "$d$pad");
print join ("*",@d), "\n";