- incr db key #!optional nprocedure
Atomically increment the value associated with key by n. n may be an integer or a floating point value, and defaults to 1.
If the value is a string, it is converted to a number if possible, and the new value will be a number. If the conversion fails, it is considered to be zero, so the resulting value will be the number n.
Returns #t if the key existed and #f if it did not.