The push keyword edit
The push function treats ARRAY as a stack by appending LIST values to ARRAY. Returns the number of elements in the ARRAY after push is completed.
From Perl 5.14.0 onwards, a scalar EXPRESSION can be passed that should hold a reference to an unblessed array. The argument is dereferenced automatically. This is a highly experimental aspect of push and may change in future Perl versions.
push ARRAY, LIST
push EXPRESSION, LIST