A nice way of keeping things together when pre-allocating arrays is to use the fact that my is a function and do the declaration and preallocation in the same statement like this.

Update: I swear it worked 10 minutes ago when I tested it.But I tried it in a perl shell, and first time I tried it I did

$#{\@a} = 50; print scalar @a; which printed 51. Great!

Then I thought "Ah! Should have used my", so I recalled the line, and added the my, and again it printed 51.........so I posted.

My little perl shell has its uses, but ......

Thanks to sauoq who brought me to book.

$#{\my @array} = 100;

</Update>

The idea can also be extended to pre-allocating hash buckets like this

keys my %hash = 2**8;
[download]

Though this is tougher to verify as if you immediatly evaluate the hash in a scalar context print scalar %hash; you get 0, which is disconcerting. However, if you then add one key to the hash  %hash= (a=>1); print scalar %hash; you get 1/256 showing that it did work but simply fails to report the fact until it has at least one key.