Replace every second character of a word in a text with a specific symbol

ReplaceCharacterWithSymbol.kt

package org.kotlinlang.play

fun main() {
    val sample = "Replace every second character of a word in a text with a specific symbol"
    val words = sample.split(" ")
    
    println(replaceCharInWords(words).joinToString(" "))
}

fun replaceCharInWords(words: List<String>, index: Int = 1, with: Char = '@'): List<String> {
    return words.map {
        if (it.length > index) {
            var chars = it.toCharArray()
            chars[index] = with
            
            return@map chars.concatToString()
        }
        return@map it
    }
}