** Summary **

increment a value in a [[`[dict]`]ionary 


** Synopsis **

    :   '''[dict] incr''' ''variable'' ''key'' ?''increment''?


** Description **

Adds the given ''increment'' value (an integer that defaults to 1 if not
specified) to the value that the given ''key'' maps to in the [dictionary]
value contained in the given ''variable'', writing the resulting dictionary
value back to that variable, and returning the value of the entire dictionary.
Non-existent keys are treated as if they map to 0. It is an error to increment
a value for an existing key if that value is not an integer.

** See also **

   * [incr]

<<categories>> Command