r.scala

    // Support implicit conversion from regex string CLI opt to matching filter function.
    implicit val scoptFilterRegexRead: scopt.Read[(String) => Boolean] = scopt.Read.reads { s =>
        val regex = s.r
        (string: String) => {
            string match {
                case regex(_*) => true
                case _ => false
            }
        }
    }

...

opt[(String) => Boolean]('w', "topic-whitelist") optional() valueName "<topic-whitelist>" action { (x, p) =>
            p.copy(topicWhitelistFilter = x)
        } text """Whitelist regex of topics imported by Camus to refine.""".stripMargin