parse.y:2559
static VALUE
lex_get_str(s)
    VALUE s;
{
    char *beg, *end, *pend;

    beg = RSTRING(s)->ptr;
    if (lex_gets_ptr) {
	if (RSTRING(s)->len == lex_gets_ptr) return Qnil;
	beg += lex_gets_ptr;
    }
    pend = RSTRING(s)->ptr + RSTRING(s)->len;
    end = beg;
    while (end < pend) {
	if (*end++ == '\n') break;
    }
    lex_gets_ptr = end - RSTRING(s)->ptr;
    return rb_str_new(beg, end - beg);
}
