Count occurrences of a substring

Built-in:

say "the three truths".count("th")
say "ababababab".count("abab")

User-created function:

func countSubstring(s, ss) {
    var re = Regex(ss.escape, 'g')      # 'g' for global
    var counter = 0
    while (s =~ re) { ++counter }
    return counter
}
 
say countSubstring("the three truths","th")
say countSubstring("ababababab","abab")

Output:

3
2