dune

(executable
 (public_name my_program))

dune-project

(lang dune 1.11)
(name my_program)

Makefile

.PHONY: build install

ifeq ($(PREFIX),)
INSTALL_FLAGS=
else
INSTALL_FLAGS=--prefix=$(PREFIX)
endif

build:
	dune build

install: build
	dune install $(INSTALL_FLAGS)

my_program.ml

let () = print_endline "hi"

my_program.opam

# Intentionally empty