ode">c2</code> (inclusively) is denoted by <code class="code">c1-c2</code>.
      Hence, <code class="code">%[0-9]</code> returns a string representing a decimal number
      or an empty string if no decimal digit is found; similarly,
      <code class="code">%[0-9a-f]</code> returns a string of hexadecimal digits.
      If a closing bracket appears in a range, it must occur as the
      first character of the range (or just after the <code class="code">^</code> in case of
      range negation); hence <code