"hello".upper()
"WORLD".lower()
"  spaces  ".trim()

[1, 2, 3].len()
[1, 2, 3, 4, 5].head()

let text = "Hello World"
text.len()

let arr = [10, 20, 30, 40]
arr.len()

"hello world".split(" ")

let name = "alice"
name.upper()

"test string".replace("test", "demo")

[5, 10, 15].map(fun(x) { x * 2 })
[1, 2, 3, 4, 5].filter(fun(x) { x > 3 })