To define custom matching, you need to define an extractor (an object with an unapply method). Implementing that requires parsing the string. Here's some code that does that using parser combinators:

case class StringAndNumber(string: String, number: Int)

object Test {
  def unapply(s: String): Option[StringAndNumber] = Parser(s)
}

object Parser extends scala.util.parsing.combinator.RegexParsers {

  def apply(s: String): Option[StringAndNumber] =
    parseAll(stringAndNumber, s) match {
      case Success(x, _) => Some(x)
      case _ => None
    }

  lazy val stringAndNumber = string ~ number ^^
    { x => StringAndNumber(x._1, x._2) }

  lazy val string = "[^0-9]*".r

  lazy val number = "[0-9]+".r ^^ { _.toInt }
}

def foo(s: String): String = s match {
  case "str" => "str"
  case Test(san) => s"${san.string}, ${san.number}"
  case _ => "?"
}
 
println {
  Seq(
    foo("str"),  // str
    foo("str2"), // str, 2
    foo("2str")  // ?
  ).mkString("\n")
}

To define custom matching, you need to define an extractor (an object with an unapply method). Implementing that requires parsing the string. Here's some code that does that using parser combinators:

case class StringAndNumber(string: String, number: Int)

object Test {
  def unapply(s: String): Option[StringAndNumber] = Parser(s)
}

object Parser extends scala.util.parsing.combinator.RegexParsers {

  def apply(s: String): Option[StringAndNumber] =
    parseAll(stringAndNumber, s) match {
      case Success(x, _) => Some(x)
      case _ => None
    }

  lazy val stringAndNumber = string ~ number ^^
    { x => StringAndNumber(x._1, x._2) }

  lazy val string = "[^0-9]*".r

  lazy val number = "[0-9]+".r ^^ { _.toInt }
}

def foo(s: String): String = s match {
  case "str" => "str"
  case Test(san) => s"${san.string}|${san.number}"
  case _ => "?"
}

// prints: "str, str|2, ?"
println ( Seq("str", "str2", "2str").map(foo(_)).mkString(", ") )