A single TCL script will usually be used to describe a complete model. Once the model is defined, it may be applied to a specific device by loading a structure from a file and running the appropriate solve command for the model.
It is best to build a model bottom up. Define TCL variables that will be used as field name aliases and model parameters first. Then define Alamode functions, operators, equations, systems, and finally the model. After the model is defined, a structure may be loaded and the model can be applied to the fields in a structure by running a solve command.