(question) fast split/join of strings

[William Park]

Hi all,

Is there fast way of splitting and joining of strings in the recent Bash 
versions?

For splitting, I'm aware of
    old="a,b,c"
    IFS=, read -a arr <<< "$old"

For joining,
    new=$(IFS=,; echo "${arr[*]}")
or
    new=$(IFS=,; echo "$*")