StringInterpolation.scala

trait InterpolationContext {
  implicit def str2interp(s: String) = new InterpolatedString(s)

  class InterpolatedString(val s: String) {
    def / = interpolate(s)
    def identifier = s.substring(2, s.length - 1)
  }

  object Tokenizer {
    def unapply(s: String): Option[Iterator[String]] = {
      Some("\\$\\{.+?\\}".r.findAllIn(s).matchData.map { (x) => x.matched })
    }
  }

  def interpolate(s: String) = {    
    var sb = s
    def evaluate(token:String):String = {
      try {
        val method = this.getClass.getMethod(token.identifier)
        method.invoke(this).toString
      } catch {
        case _: NoSuchMethodException => token
      }
    }    
    s match {
      case Tokenizer(tokens) => tokens.foreach { (x:String) => sb = sb.replace(x, evaluate(x)) }
    }
    sb
  }
}

object Test extends InterpolationContext {
  val a = "3"
  def main(args: Array[String]) {
    println("expanded: ${a}; not expanded: ${b}; more text"/)
  }
}