Prefix and postfix elements of a bash array

Bash brace expansion don’t use regexes. The pattern used is just some shell glob, which you can find in bash manual 3.5.8.1 Pattern Matching.

Your two-step solution is cool, but it needs some quotes for whitespace safety:

ARR_PRE=("${ARRAY[@]/#/prefix_}")
echo "${ARR_PRE[@]/%/_suffix}"

You can also do it in some evil way:

eval "something $(printf 'pre_%q_suf ' "${ARRAY[@]}")"