var fmt = String(JSON.stringify(format))
  var js = '  "use strict"\n  return ' + fmt.replace(/:([-\w]{2,})(?:\[([^\]]+)\])?/g, function (_, name, arg) {
    var tokenArguments = 'req, res'
    var tokenFunction = 'tokens[' + String(JSON.stringify(name)) + ']'

    if (arg !== undefined) {
      tokenArguments += ', ' + String(JSON.stringify(arg))
    }

    return '" +\n    (' + tokenFunction + '(' + tokenArguments + ') || "-") + "'
})

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