+ || (*prev == '|' && (syntax & RE_NO_BK_VBAR || prev_prev_backslash))
+ /* After a shy subexpression? */
+ || ((syntax & RE_SHY_GROUPS) && prev - 2 >= pattern
+ && prev[-1] == '?' && prev[-2] == '('
+ && (syntax & RE_NO_BK_PARENS
+ || (prev - 3 >= pattern && prev[-3] == '\\')));