Get all hierarchical instances in the top level module (LLM: hierarchical instances) Usage: my @instances = get_instances($pattern); $pattern: Match pattern, can have wildcard "*", if it is empty, it is treated as "*" @instances: Array of the hierarchical instances Examples: @instances = get_instances("UI_*"); # Any hierarchical instances with UI_ as prefix. @instances = get_instances; # All hierarchical instances.