This list has one list-specific operation: Trace Variable creates a new toplevel window that will contain set statements reflecting writes to the variable. (The trace will contain the last 50 set's by default, the number can be set through the *Variable_trace.savelines option.) Trace Variable handles both scalars and arrays.
For an interesting example of how this works, try the following:
The default list of patterns for the list filter is:
^tkPriv.* ^auto_.* ^tk_.*And is read from the option *Globals_list.patterns.