A Perl reference is a fundamental data type that “points” to another piece of data or code. A reference knows the location of the information and the type of data stored there.

A reference is a scalar and can be used anywhere a scalar can be used. Any array element or hash value can contain a reference (a hash key cannot contain a reference), which is how nested data structures are built in Perl. You can construct lists containing references to other lists, which can contain references to hashes, and so on.