!*$
 * M[getopt] -> Success|Failure -- Parse options
 *
 * Parses command line options according to the string
 * \(lqoptstring\(rq, similar to \fBgetopt\P(3).
 * \(lqoptstring\(rq is a list of single character
 * option names.
 * If followed by a colon, the option takes an argument
 * (which can be part of the same command line argument as in
 * \(lq-Ofoo\(rq).
 * If followed by two colons, the option argument is optional.
 * For every detected option \fIX\fP, a register \fBgetopt.\fIX\fR is
 * defined with -1 (true) in its integer part.
 * If the option had an argument, it is stored in the register's
 * string part.
 *
 * A condition boolean is returned to signify whether
 * there was a parsing error.
 *!
[optstring]
@[getopt]{
  .U.d
  <
    .-Z"= 1; ' 0A-^^-"N :L; F< '

    1A-^^-"= K 1; '

    0U.i <
      :Q[optstring]-Q.i"= Q.dJ 0 '
      Q.iQ[optstring]U.c

      0U.#ar <
        %.i-:Q[optstring]"= 1; '
        Q.iQ[optstring]-^^:"N 1; '
      %.#ar>

      1A-Q.c"=
        -U[getopt.U.c]
        Q.#ar">
          2A-10"=
            K Q.#ar-1"> 0A-^^-"= 0U.i F< ' '
          |
            2D
          '
          LR 0X[getopt.U.c] 0L
        '
        K 1;
      '
    >
  >
  Q.dJ
-1}