@shift_map(m:map, n:numeric)


build a new map containing the entries of m that have a integer key with n added. For example:

       $m := MAP{ (1, 1), ("a", 1), (1.0, 1) (2, 2), ("b", 2), (2.0, 2) } print (@shift_map($m, 11))


displays MAP{ (12, 1), (13, 2) }.