#!/usr/bin/perl

use strict;
use warnings; 

my @A = ( 1 .. 3, 'abc', 'zz', 79, 444 );
my $A = join ',', @A;

print "# With 'undef's:\n";

for my( $i, $j, $k )( @A ){
	print "[$i-$j-$k]";
	}
print "\n";

for( my $i = 0; $i < @A; $i += 3 ){
	print "[$A[ $i ]-$A[ $i + 1 ]-$A[ $i + 2 ]]";
	}
print "\n";

print "Without 'undef's -- no stepping out of an array:\n";

for my $i ( grep $_ % 3 == 0, 0 .. @A - 3 ){
	print "[$A[ $i ]-$A[ $i + 1 ]-$A[ $i + 2 ]]";
	}
print "\n";

$A =~ m/
	\b([^,]+)\b,
	\b([^,]+)\b,(*SKIP)
	\b([^,]+)\b
	(?{ print "[$1-$2-$3]" })
	(*FAIL)
	/x;
print "\n";