# [Scala](https://scala-lang.org), 73 bytes

<!-- language: lang-scala -->

    (s:String)=>"(\\d+)(.)".r.replaceSomeIn(s,m=>Some("$2"*m.group(1).toInt))

[Try it online!](https://scastie.scala-lang.org/BF2fTBqJTfmB7BTR9OXa6w)