Switch to raw string.

day03.kts

@@ -9,7 +9,7 @@ var doState = true
 
 while (scanner.hasNextLine()) {
     val line = scanner.nextLine()
-    val regex = Regex("(mul\\((\\d+),(\\d+)\\))|(do\\(\\))|(don't\\(\\))")
+    val regex = Regex("""(mul\((\d+),(\d+)\))|(do\(\))|(don't\(\))""")
     val match = regex.findAll(line)
     for (matchResult in match) {
         if (matchResult.value == "don't()") {