See the current Perl documentation for push.

Here is our local, out-dated (pre-5.6) version:

push - append one or more elements to an array


Treats ARRAY as a stack, and pushes the values of LIST onto the end of ARRAY. The length of ARRAY increases by the length of LIST. Has the same effect as

    for $value (LIST) {
        $ARRAY[++$#ARRAY] = $value;

but is more efficient. Returns the new number of elements in the array.