#!/bin/bash

curl "http://www.hashcash.org/source/" 2> /dev/null | \
  tr "\"" "\n" | \
  grep "^hashcash-[0-9.-]*\.tgz\$" | \
  sed "s|^hashcash-\(.*\)\.tgz\$|\1|" | \
  sort -V | \
  tail -n1