strings.Count

If SUBSTR is an empty string, this function returns 1 plus the number of Unicode code points in STRING.

{{ "aaabaab" | strings.Count "a" }} → 5
{{ "aaabaab" | strings.Count "aa" }} → 2
{{ "aaabaab" | strings.Count "aaa" }} → 1
{{ "aaabaab" | strings.Count "" }} → 8