Matches a subject against the pattern,
returns an array where the first element are the whole match,
and the subsequent are the matching subpatterns.
Returns 0 if there was no match.
example:
> Regexp.PCRE.Plain("i\(.*\) is \(.*\)u")->split2("pike is fun");
Result: ({
"ike is fu",
"ke",
"f"
})