The regexp_match function returns a copy of substring of string str which matches the regular
expression pattern. Previous behavior of this function would cut the first characters of str until the end of regular
expression matched substring. In this way str could be passed to this function again to find the next occurrence of
substring that matches the regular expression. By default this behavior is not adopted by this function, but can be
enabled for pre 3.2 compatibility by supplying the optional third parameter. If either the pattern or str parameter
contain wide characters this function will operate in wide mode, first converting any narrow characters to wide and
returning a wide character response. Otherwise this function operates in narrow mode by default.