There's still one problem. To exemplify it, if you call with `-av`, it'll process the `v` as the option `-v` instead of the option value to `-a`. If you only have one possible option that takes a value, this can be fixed by putting its case clause before all others. If you have more, then that'll require things to get a little more complicated:

      -d*|-[!-]*d*|--debug)
        if [[ ! "$finished_case" && ("$1" = --debug || "$1" =~ '^[^ad]*d') ]]; then
          debug=true
        fi
      ;;&

      -a*|-[!-]*a*|--arg)
        if [[ ! "$finished_case" && ("$1" = --arg || "$1" =~ '^[^a]*a') ]]; then
          if [[ "$1" != --arg ]]; then
            value="${1#*a}"
          fi
          if [[ ! "$value" ]]; then
            value="$2"
            shift
          fi
          finished_case=true
        fi
      ;;&
      ...
    esac

    shift
    finished_case=
  done

All case-clauses would need to use `;;&` by the way, including `-v` and `-h`. The regex is generally:

  "^[^${all_options_with_values}${current_option}]*${current_option}"

Another problem is that option and argument non-recognition would not work as previously layed out. You can include short options that aren't recognized, and they'll be ignored instead of raising errors. For positional arguments, one would need a condition to check for options, since using `;;&` for everything means that everything would land to

  *)

Maybe those are the last issues, but this is already out of hand for otherwise small and simple shell scripts. All these complications arise from trying to support the sticking together of short options and their possible values. Processing arguments in a case loop is much, much simpler if we avoid supporting those 2 features.