Place the following in a rule to dump the current match object

{{ _dumper(match) }}

Place the following in a rule to dump the call stack of rule that got you to this point

{{ backtrace }}

use the <panic> rule to die and dump a backtrace of your current location in the parse rules

<panic>

use whitespace caching

token ws {
  | <?{{  $P0 = get_global '$!ws'
          if null $P0 goto noshort
          $P1 = $P0.'to'()
          $P2 = match.'to'()
          if $P1 != $P2 goto noshort
          .return (1)
        noshort:
          set_global '$!ws', match
          .return (0)
  }}>
  | <!ww> <ws_all>+
  | <ws_all>*
}