#!/usr/bin/perl
use strict;
use warnings;
my @a = qw/one two three four five six seven /;
$~ = "TEST";
print "---+++---\n";
my ($a1, $a2, $a3);
while (@a) {
  $a1 = shift @a || "empty";
  $a2 = shift @a || "empty";
  $a3 = shift @a || "empty";
  write;
}
print "---------\n";
format TEST =
a: @* @* @*
   $a1, $a2, $a3
.