func (re Regexp) FindSubmatch(s string) []string {
	return re.r.FindStringSubmatch(s)
}
FindSubmatch returns a slice of strings holding the text of the leftmost
match of the regular expression in s and the matches, if any, of its
subexpressions, as defined by the 'Submatch' description in the Go regexp
package comment. A return value of nil indicates no match.
package builtin
import (
	"regexp"
)
type Regexp struct {
	r *regexp.Regexp
}
func (re Regexp) Match(s string) bool {
	return re.r.MatchString(s)
}
func (re Regexp) Find(s string) string {
	return re.r.FindString(s)
}
func (re Regexp) FindAll(s string, n int) []string {
	return re.r.FindAllString(s, n)
}
func (re Regexp) FindAllSubmatch(s string, n int) [][]string {
	return re.r.FindAllStringSubmatch(s, n)
}