Comment by aozgaa

Another solution to the pipeline example, this time making use of a subprogram for the frequency/accumulation:

    < README.md \
      tr -c '[:alpha:]' '\n' \
    | tr '[:upper:]' '[:lower:]' \
    | awk '
        NF {
          if (!($0 in count)) order[++n] = $0
          count[$0]++
        }
        END {
          for (i = 1; i <= n; i++) {
            print count[order[i]], order[i]
          }
        }
    '

If you don't allow `awk` in your "pure bash" then ofc this is not satisfactory. But it has the upside that the associative arrays are pretty explicit data structures (for the ordering and counts, respectively).