-- String-case builtins: `upr` (uppercase), `lwr` (lowercase),
-- `cap` (capitalise first char, leave the rest unchanged).
-- ASCII-only for the first cut.
upr-demo>t;upr "hello world"
lwr-demo>t;lwr "HELLO WORLD"
cap-demo>t;cap "hello world"
-- run: upr-demo
-- out: HELLO WORLD
-- run: lwr-demo
-- out: hello world
-- run: cap-demo
-- out: Hello world