diff --git a/internal/lazyregexp/lazyregexp.go b/internal/lazyregexp/lazyregexp.go
new file mode 100644
index 0000000000..6334edb60d
--- /dev/null
+++ b/internal/lazyregexp/lazyregexp.go
@@ -0,0 +1,90 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code below was largely copied from golang.org/x/mod@v0.22;
+// https://github.com/golang/mod/blob/v0.22.0/internal/lazyregexp/lazyre.go
+// with some additional methods added.
+
+// 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
+}
+
+func (r *Regexp) re() *regexp.Regexp {
+	r.once.Do(r.build)
+	return r.rx
+}
+
+func (r *Regexp) build() {
+	r.rx = regexp.MustCompile(r.str)
+	r.str = ""
+}
+
+func (r *Regexp) FindSubmatch(s []byte) [][]byte {
+	return r.re().FindSubmatch(s)
+}
+
+func (r *Regexp) FindAllStringSubmatch(s string, n int) [][]string {
+	return r.re().FindAllStringSubmatch(s, n)
+}
+
+func (r *Regexp) FindStringSubmatch(s string) []string {
+	return r.re().FindStringSubmatch(s)
+}
+
+func (r *Regexp) FindStringSubmatchIndex(s string) []int {
+	return r.re().FindStringSubmatchIndex(s)
+}
+
+func (r *Regexp) ReplaceAllString(src, repl string) string {
+	return r.re().ReplaceAllString(src, repl)
+}
+
+func (r *Regexp) FindString(s string) string {
+	return r.re().FindString(s)
+}
+
+func (r *Regexp) FindAllString(s string, n int) []string {
+	return r.re().FindAllString(s, n)
+}
+
+func (r *Regexp) MatchString(s string) bool {
+	return r.re().MatchString(s)
+}
+
+func (r *Regexp) ReplaceAllStringFunc(src string, repl func(string) string) string {
+	return r.re().ReplaceAllStringFunc(src, repl)
+}
+
+func (r *Regexp) SubexpNames() []string {
+	return r.re().SubexpNames()
+}
+
+var inTest = len(os.Args) > 0 && strings.HasSuffix(strings.TrimSuffix(os.Args[0], ".exe"), ".test")
+
+// New creates a new lazy regexp, delaying the compiling work until it is first
+// needed. If the code is being run as part of tests, the regexp compiling will
+// happen immediately.
+func New(str string) *Regexp {
+	lr := &Regexp{str: str}
+	if inTest {
+		// In tests, always compile the regexps early.
+		lr.re()
+	}
+	return lr
+}
diff --git a/internal/lazyregexp/lazyregexp_test.go b/internal/lazyregexp/lazyregexp_test.go
new file mode 100644
index 0000000000..898ea0b437
--- /dev/null
+++ b/internal/lazyregexp/lazyregexp_test.go
@@ -0,0 +1,23 @@
+package lazyregexp
+
+import (
+	"testing"
+)
+
+func TestCompileOnce(t *testing.T) {
+	t.Run("invalid regexp", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r == nil {
+				t.Errorf("expected a panic")
+			}
+		}()
+		_ = New("[")
+	})
+	t.Run("valid regexp", func(t *testing.T) {
+		re := New("[a-z]")
+		ok := re.MatchString("hello")
+		if !ok {
+			t.Errorf("expected a match")
+		}
+	})
+}