use strict;
use warnings;
use Data::Dumper ();

my @rocks = ();
$rocks[0] = 'bedrock';
$rocks[1] = 'slate';
$rocks[2]= 'lava';
$rocks[3] = 'crushed rock';

print Data::Dumper::Dumper(\@rocks);

$rocks[99] = 'schist';

print Data::Dumper::Dumper(\@rocks);

$#rocks = 2; # forget all rocks after 'lava'
print Data::Dumper::Dumper(\@rocks);

$#rocks = 99; # add 97 undef e
print Data::Dumper::Dumper(\@rocks);