Why would someone want to learn Unix Programming using OCAML? Not a smart choice. Also this does not look easier to read than a shell script either.

let rec copy_rec source dest = let infos = lstat source in match infos.st_kind with | S_REG -> file_copy source dest; set_infos dest infos | S_LNK -> let link = readlink source in symlink link dest | S_DIR -> mkdir dest 0o200; Misc.iter_dir (fun file -> if file <> Filename.current_dir_name && file <> Filename.parent_dir_name then copy_rec (Filename.concat source file) (Filename.concat dest file)) source; set_infos dest infos | _ -> prerr_endline ("Can't cope with special file " ^ source)