In factor(), where we handle names:

    if (is_letter(cur())) {
        const name: []const u8 = read_name();
        if (cur() == '(') {
            pos += 1;
            skip();
            var args: [8]i64 = undefined;
            var ac: usize = 0;
            while (cur() != ')' and cur() != 0) {
                args[ac] = expression();
                ac += 1;
                if (cur() == ',') { pos += 1; skip(); }
            }
            if (cur() == ')') { pos += 1; skip(); }
            return call_fn(name, &args, ac);
        }
        return getVar(name);
    }

var save_vn: [32][256][]const u8 = undefined;
var save_vv: [32][256]i64 = undefined;
var save_nv: [32]usize = undefined;
var save_depth: usize = 0;

fn call_fn(name: []const u8, args: *const [8]i64, ac: usize) i64 {
    _ = ac;
    // Find function
    var fi: usize = 0;
    while (fi < fn_count) {
        if (streq(fn_names[fi], name)) { break; }
        fi += 1;
    }
    if (fi >= fn_count) { return 0; }
    // Save caller state
    const d: usize = save_depth;
    save_nv[d] = num_vars;
    const saved_pos: usize = pos;
    for (0..num_vars) |i| {
        save_vn[d][i] = var_names[i];
        save_vv[d][i] = var_values[i];
    }
    save_depth += 1;
    // Bind parameters
    num_vars = 0;
    for (0..fn_pcounts[fi]) |i| {
        setVar(fn_params[fi][i], args[i]);
    }
    // Execute body
    pos = fn_starts[fi];
    return_flag = false;
    const result: i64 = exec_block();
    // Restore
    save_depth -= 1;
    pos = saved_pos;
    num_vars = save_nv[d];
    for (0..num_vars) |i| {
        var_names[i] = save_vn[d][i];
        var_values[i] = save_vv[d][i];
    }
    return_flag = false;
    return result;
}