docs: function replaceSpermies (version) {
    return version.trim().replace(expressions.parseSpermy,
                                  function (v, gtlt, M, m, p) {
      if (gtlt) throw new Error(
        "Using '"+gtlt+"' with ~ makes no sense. Don't do it.")
      if (!M || M.toLowerCase() === "x") {
        return "*"
      }
      if (!m || m.toLowerCase() === "x") {
        return ">="+M+".0.0 <"+(+M+1)+".0.0"
      }
      if (!p || p.toLowerCase() === "x") {
        return ">="+M+"."+m+".0 <"+M+"."+(+m+1)+".0"
      }
      return ">="+M+"."+m+"."+p+" <"+M+"."+(+m+1)+".0"
    })
  }