eval_leader(char_u **arg, int vim9)
{
    char_u	*s = *arg;
    char_u	*p = *arg;

    while (*p == '!' || *p == '-' || *p == '+')
    {
	char_u *n = skipwhite(p + 1);

	// ++, --, -+ and +- are not accepted in Vim9 script
	if (vim9 && (*p == '-' || *p == '+') && (*n == '-' || *n == '+'))
	{
	    semsg(_(e_invalid_expression_str), s);
	    return FAIL;
	}
	p = n;
    }
    *arg = p;
    return OK;
}
eval_leader(char_u **arg, int vim9)
{
    char_u	*s = *arg;
    char_u	*p = *arg;

    while (*p == '!' || *p == '-' || *p == '+')
    {
	char_u *n = skipwhite(p + 1);

	 
	if (vim9 && (*p == '-' || *p == '+') && (*n == '-' || *n == '+'))
	{
	    semsg(_(e_invalid_expression_str), s);
	    return FAIL;
	}
	p = n;
    }
    *arg = p;
    return OK;
}