autovivication basically means that datastructures are automatically expanded at first use.

For instance, if you've got a hash and access a not previously instantiated element and treat it like a hash reference, a hash reference will be created for you:

#!/usr/bin/perl -w
use strict;

my %hash = ();
$hash{a}->{b} = 1;
print $hash{a}->{b};
[download]

This means you need to do less explicit typing/instantiating, at the cost of possibly accidentally creating structures that aren't there when you mistype.

Note that perl will still throw an error when you for example treat a hash reference as an array reference, so there's still some checking going on.

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