} else {
		regexp.prefix, regexp.prefixComplete, regexp.prefixEnd = onePassPrefix(prog)
	}
	if regexp.prefix != "" {
		// TODO(rsc): Remove this allocation by adding
		// IndexString to package bytes.
		regexp.prefixBytes = []byte(regexp.prefix)
		regexp.prefixRune, _ = utf8.DecodeRuneInString(regexp.prefix)
	}

	n := len(prog.Inst)
	i := 0
	for matchSize[i] != 0 && matchSize[i] < n {
		i++
	}

package syntax

// Note to implementers:
// In this package, re is always a *Regexp and r is always a rune.

import (
	"slices"
	"strconv"
	"strings"
	"unicode"
)

// A Regexp is a node in a regular expression syntax tree.
type Regexp struct {
	Op       Op // operator
	Flags    Flags
	Sub      []*Regexp  // subexpressions, if any
	Sub0     [1]*Regexp // storage for short Sub

// Package lazyregexp is a thin wrapper over regexp, allowing the use of global
// regexp variables without forcing them to be compiled at init.
package lazyregexp

import (
	"os"
	"regexp"
	"strings"
	"sync"
)

// Regexp is a wrapper around [regexp.Regexp], where the underlying regexp will be
// compiled the first time it is needed.
type Regexp struct {
	str  string
	once sync.Once
	rx   *regexp.Regexp

	fmt.Println(matched, err)
	matched, err = regexp.MatchString(`bar.*`, "seafood")
	fmt.Println(matched, err)
	matched, err = regexp.MatchString(`a(b`, "seafood")
	fmt.Println(matched, err)
	// Output:
	// true <nil>
	// false <nil>
	// false error parsing regexp: missing closing ): `a(b`
}

func ExampleQuoteMeta() {
	fmt.Println(regexp.QuoteMeta(`Escaping symbols like: .+*?()|[]{}^$`))

}

// Takes a list of strings and compiles them into a list of regular expressions
func compileRegexps(regexpStrings []string) ([]*regexp.Regexp, error) {
	regexps := []*regexp.Regexp{}
	for _, regexpStr := range regexpStrings {
		r, err := regexp.Compile(regexpStr)
		if err != nil {
			return []*regexp.Regexp{}, err
		}
		regexps = append(regexps, r)
	}
	return regexps, nil

package profile

import (
	"fmt"
	"regexp"
	"strings"
)

var (
	reservedNames = []string{"(anonymous namespace)", "operator()"}
	bracketRx     = func() *regexp.Regexp {
		var quotedNames []string
		for _, name := range append(reservedNames, "(") {
			quotedNames = append(quotedNames, regexp.QuoteMeta(name))
		}
		return regexp.MustCompile(strings.Join(quotedNames, "|"))
	}()
)

[short] skip

go test -short -coverpkg=strings strings regexp
! stdout '[^0-9]0\.0%'
stdout  'strings.*coverage:.*[1-9][0-9.]+%'
stdout  'regexp.*coverage:.*[1-9][0-9.]+%'

go test -short -cover strings math regexp
! stdout '[^0-9]0\.0%'
stdout  'strings.*coverage:.*[1-9][0-9.]+%'
stdout  'math.*coverage:.*[1-9][0-9.]+%'

			t.Errorf("Parse(%#q, Perl): %v", regexp, err)
		}
		if re, err := Parse(regexp, POSIX); err == nil {
			t.Errorf("Parse(%#q, POSIX) = %s, should have failed", regexp, dump(re))
		}
	}
	for _, regexp := range onlyPOSIX {
		if re, err := Parse(regexp, Perl); err == nil {
			t.Errorf("Parse(%#q, Perl) = %s, should have failed", regexp, dump(re))
		}
		if _, err := Parse(regexp, POSIX); err != nil {

			WantException:  false,
		},
		{ // case 4
			Args:           strings.Split("envoy --browser=false", " "),
			ExpectedRegexp: regexp.MustCompile(".*Error: specify a pod or --selector"),
			WantException:  true,
		},
		{ // case 5
			Args:           strings.Split("envoy --browser=false pod-123456-7890", " "),
			ExpectedRegexp: regexp.MustCompile("http://localhost:3456"),
			WantException:  false,

// matches.
func repeated(res ...*regexp.Regexp) *regexp.Regexp {
	return match(group(expression(res...)).String() + `+`)
}

// group wraps the regexp in a non-capturing group.
func group(res ...*regexp.Regexp) *regexp.Regexp {
	return match(`(?:` + expression(res...).String() + `)`)
}

// capture wraps the expression in a capturing group.