#!/usr/bin/perl -w

$arr[0]='a';
$arr[1]='b';
$arr[2]='c';
$arr[3]='d';
delete $arr[1];
delete $arr[2];

print join(" ", map { defined() ? $_ : '[undef]' } @arr),"\n";;

##</code><code>##

#!/usr/bin/perl -w

$arr[0]='a';
$arr[3]='d';

print join(" ", map { defined() ? $_ : '[undef]' } @arr),"\n";

##</code><code>##

a [undef] [undef] d