The simulator uses variables in certain places to allow you to change its
behavior at runtime. The set and print commands work on these
variables.
All variables are fundamentally of type int. There is no support for strings.
Simulator modules declare variables in the usual way, then export these to the
variable tracker using conf_add. This associates a public name for the variable
that the command language sees. When variables are modified in this way, the module's
int variables are then modified directly.