incr0 — increment a variable or set it to 1 if nonexistent.
varname? ?num?
                Increment a variable
                varname by
                num.  If the
                variable doesn't exist, create it instead of returning an
                error.
            
| ![[Note]](images/note.png) | Note | 
|---|---|
| incr0 functionality is provided by the native incr in Tcl >= 8.5, therefore this command is deprecated and kept as an interpreter alias only for compatibility. As such incr0 wasn't moved to the ::rivet namespace and it will be removed in future versions of Rivet. |