I need help with understanding with a piece code

Hello, my name is Michael and I am currently working on a matlab heavy project. The project is a matlab compiler for compiling Simulink programs, created with project intern library, into assembler. My predecessor wrote the compiler, but sadly he didn't comment very well the source code and I can't contact him. So, he worte a function in his compiler, which creates the assembler source code file. In this function he builds an optimisation method, with which, he reduces the number of used variables. I need help with understanding this piece of code, so I came here, looking for help. Here is the code snippet:

     if ~strcmp(graph(name).type, 'Outport')
            % reduce number of used variable
            % default variable name
            signal_name = node.arguments{3};

            % replace variable when flag is set and not needed for Mov & Mov_*
            if optimizing && OPTIMISATIONS('reduce_variables') && ...
                    ~strcmp('Mov', node.type(1:3)) && ~strcmp(node.arguments{3}, '?')   
                % check if a free name is available
                for key = refs.keys
                    var_name = key{1};
                    % check if variable is free for reusage
                    % only constants can have negative ref counts
                    if refs(var_name) < 1 && var_name(1) ~= '_'
                        signal_name = var_name;
                        break;
                    end
                end
            end
            % special case for i.e. wbnone
            if ~strcmp(signal_name, '?')
                % determine number of references to signal_names
                % to avoid code duplicate often overwritten input arguments
                ref_add = update_references(graph, node.arguments{3}, node.next, ...
                    signal_name);
                refs(signal_name) = ref_add;
                node.arguments{3} = signal_name;
            end
        end
  end

Thanks for help and greetings from Germany.