efficient way to use matched string in variable substitution

[L A Walsh]

Starting with a number N, is there
an easy way to print its digits into an array?
I came up with a few ways, but thought this
would be nice (with '\1' or '$1' being what was matched
in the 1st part), this could be statement:

arr=(${N//[0-9]/\1 })
 or
arr=(${N//[0-9]/$1 })

Instead of using loops (my=declare):

>  n=988421
>  for x in 0 1 2 3 4 5 6 7 8 9;do n=${n//$x/$x }; done
>  arr=($n)
>  my -p arr
declare -a arr=([0]="9" [1]="8" [2]="8" [3]="4" [4]="2" [5]="1")

or w/substrings:

>  for ((d=0; d<${#n};d+=1)); do arr+=(${n:$d:1}); done
>  my -p arr
declare -a arr=([0]="9" [1]="8" [2]="8" [3]="4" [4]="2" [5]="1")

Not a big thing, but having some way for the match of an RE
to be specified in the output would be handy...