Autovivification is an unusual feature of the Perl programming language having to do with the dynamic creation of data structures. Trying to access an element of a hash (associative array) or array that does not already exist creates both the hash or array, and all elements below the given index for the array.

This is in contrast to most other high level languages, in which you must explicitly create a given hash or array before you use it. This includes Python, PHP, JavaScript and all the C style languages.