Perl builds complex datastructures based on references. Any element of a hash or array, or any scalar may contain a reference to another hash, array, or scalar (among other things). This is the basis for defining custom made datastructures. For further info, see perlref, perlreftut, perllol, and perldsc.

Perl also allows for the creation of classes and object instances based on those classes. See perlobj, perlboot, ...and there are others, but that's more than enough to get you started.