at the end, this code echos  "JKC: -><-", so $last_scrub is empty. why?


    echo $scrub_list | while read scrub_entry; do
        scrub_date=$(echo $scrub_entry | awk '{print $1}')

        # was this scrub history entry a scrub -s?
        is_stop=0
        echo $scrub_entry | egrep -q " *-s *"

        if [ "$?" = "0" ]; then
            echo "found scrub -s: $scrub_entry"
            is_stop=1
        else
            echo "found scrub: $scrub_entry"
        fi

        # if 1st time (e.g. $last_scrub is empty), then set
        #   last_scrub and continue
        if [ -z $last_scrub ]; then
            if [ "$is_stop" = "0" ]; then
                echo "INIT(last_scrub) = $scrub_date"
                last_scrub=$scrub_date
            fi
            # else:  if the first entry is a scrub -s (would this ever happen?) just continue
            continue
        else
            echo "last_scrub was previously set to: $scrub_date"
            # last_scrub was already set.

            # check if scrub -s, in which case we set the last scrub to the previous
            if [ "$is_stop" = "1" ]; then
                echo "THIS is a scrub -s"
                if [ -z $second_to_last_scrub ]; then
                    # no prior successful scrub
                    echo "NO PREVIOUS SUCCESSFUL SCRUB, BLANK IT"
                    last_scrub=""
                else
                    echo "REUSE PREVIOUS SUCCESSFUL SCRUB: $second_to_last_scrub"
                    last_scrub=$second_to_last_scrub
                fi
            else
                echo "NORMAL SCRUB, UPDATE second_to_last_scrub=$last_scrub and last_scrub=$scrub_date"
                # regular scrub, update last and second_to_last
                second_to_last_scrub=$last_scrub
                last_scrub=$scrub_date
            fi
        fi

    done

    echo "JKC: ->$last_scrub<-"