When you are trying to figure out how to access a part of a complex data structure, it is important to pay attention to each level of curly brace { and square bracket [. If you look carefully you should see a square brace next to {properties}. That means that hash member is storing an array reference. Within the array are a series of {...}. Each of those are array elements. Since the array element with the property name 'maxEngines' is in the first array element, you would access its associated value like this:
$license->{properties}->[0]->{value} 