#!/usr/bin/env bash
#              ^^^^ - note bash; not zsh, not sh
 
processLine() {
  local data idx      # declare locals so we don't pollute global namespace
  local -a arr1 arr2  # declare local arrays separately
  data=$1             # assign our first positional argument to $data
 
  # no separator? bail out early
  [[ $data = *" | "* ]] || {
    echo "ERROR: Data not in expected form" >&2
    return 1
  }
 
  # break our two variables into two separate arrays
  IFS=, read -r -a arr1 <<<"${data%%' | '*}"
  IFS=, read -r -a arr2 <<<"${data#*' | '}"
 
  # iterate over those arrays by index/key to pair items up
  for idx in "${!arr1[@]}"; do
    printf '%s,%s ' "${arr1[$idx]}" "${arr2[$idx]}"
  done
  printf '\n'  # add a trailing newline
}
 
processLine 'a,b,c,d,e,f,g | 1,2,3,4,5,6,7'

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