caddyhttp: Escaping placeholders in CEL, add `vars` and `vars_regexp` (#6594)

* caddyhttp: Escaping placeholders in CEL

* Simplify some of the test cases

* Implement vars and vars_regexp in CEL

* dupl lint is dumb

* Better consts for the placeholder CEL shortcut

* Bump CEL version, register a few extensions

* Refactor s390x test script for readability

* Add retries for s390x to smooth over flakiness

* Switch to `ph` for the CEL shortcut (match it in templates cause why not)

7 files changed, 242 insertions, 52 deletions

diff --git a/modules/caddyhttp/celmatcher.go b/modules/caddyhttp/celmatcher.go
index a5565eb98..2a03ebba7 100644
--- a/modules/caddyhttp/celmatcher.go
+++ b/modules/caddyhttp/celmatcher.go
@@ -126,6 +126,10 @@ func (m *MatchExpression) Provision(ctx caddy.Context) error {
 	// light (and possibly naïve) syntactic sugar
 	m.expandedExpr = placeholderRegexp.ReplaceAllString(m.Expr, placeholderExpansion)
 
+	// as a second pass, we'll strip the escape character from an escaped
+	// placeholder, so that it can be used as an input to other CEL functions
+	m.expandedExpr = escapedPlaceholderRegexp.ReplaceAllString(m.expandedExpr, escapedPlaceholderExpansion)
+
 	// our type adapter expands CEL's standard type support
 	m.ta = celTypeAdapter{}
 
@@ -159,14 +163,17 @@ func (m *MatchExpression) Provision(ctx caddy.Context) error {
 
 	// create the CEL environment
 	env, err := cel.NewEnv(
-		cel.Function(placeholderFuncName, cel.SingletonBinaryBinding(m.caddyPlaceholderFunc), cel.Overload(
-			placeholderFuncName+"_httpRequest_string",
+		cel.Function(CELPlaceholderFuncName, cel.SingletonBinaryBinding(m.caddyPlaceholderFunc), cel.Overload(
+			CELPlaceholderFuncName+"_httpRequest_string",
 			[]*cel.Type{httpRequestObjectType, cel.StringType},
 			cel.AnyType,
 		)),
-		cel.Variable("request", httpRequestObjectType),
+		cel.Variable(CELRequestVarName, httpRequestObjectType),
 		cel.CustomTypeAdapter(m.ta),
 		ext.Strings(),
+		ext.Bindings(),
+		ext.Lists(),
+		ext.Math(),
 		matcherLib,
 	)
 	if err != nil {
@@ -247,7 +254,7 @@ func (m MatchExpression) caddyPlaceholderFunc(lhs, rhs ref.Val) ref.Val {
 		return types.NewErr(
 			"invalid request of type '%v' to %s(request, placeholderVarName)",
 			lhs.Type(),
-			placeholderFuncName,
+			CELPlaceholderFuncName,
 		)
 	}
 	phStr, ok := rhs.(types.String)
@@ -255,7 +262,7 @@ func (m MatchExpression) caddyPlaceholderFunc(lhs, rhs ref.Val) ref.Val {
 		return types.NewErr(
 			"invalid placeholder variable name of type '%v' to %s(request, placeholderVarName)",
 			rhs.Type(),
-			placeholderFuncName,
+			CELPlaceholderFuncName,
 		)
 	}
 
@@ -275,7 +282,7 @@ var httpRequestCELType = cel.ObjectType("http.Request", traits.ReceiverType)
 type celHTTPRequest struct{ *http.Request }
 
 func (cr celHTTPRequest) ResolveName(name string) (any, bool) {
-	if name == "request" {
+	if name == CELRequestVarName {
 		return cr, true
 	}
 	return nil, false
@@ -457,15 +464,15 @@ func CELMatcherDecorator(funcName string, fac CELMatcherFactory) interpreter.Int
 		callArgs := call.Args()
 		reqAttr, ok := callArgs[0].(interpreter.InterpretableAttribute)
 		if !ok {
-			return nil, errors.New("missing 'request' argument")
+			return nil, errors.New("missing 'req' argument")
 		}
 		nsAttr, ok := reqAttr.Attr().(interpreter.NamespacedAttribute)
 		if !ok {
-			return nil, errors.New("missing 'request' argument")
+			return nil, errors.New("missing 'req' argument")
 		}
 		varNames := nsAttr.CandidateVariableNames()
-		if len(varNames) != 1 || len(varNames) == 1 && varNames[0] != "request" {
-			return nil, errors.New("missing 'request' argument")
+		if len(varNames) != 1 || len(varNames) == 1 && varNames[0] != CELRequestVarName {
+			return nil, errors.New("missing 'req' argument")
 		}
 		matcherData, ok := callArgs[1].(interpreter.InterpretableConst)
 		if !ok {
@@ -524,7 +531,7 @@ func celMatcherStringListMacroExpander(funcName string) cel.MacroFactory {
 				return nil, eh.NewError(arg.ID(), "matcher arguments must be string constants")
 			}
 		}
-		return eh.NewCall(funcName, eh.NewIdent("request"), eh.NewList(matchArgs...)), nil
+		return eh.NewCall(funcName, eh.NewIdent(CELRequestVarName), eh.NewList(matchArgs...)), nil
 	}
 }
 
@@ -538,7 +545,7 @@ func celMatcherStringMacroExpander(funcName string) parser.MacroExpander {
 			return nil, eh.NewError(0, "matcher requires one argument")
 		}
 		if isCELStringExpr(args[0]) {
-			return eh.NewCall(funcName, eh.NewIdent("request"), args[0]), nil
+			return eh.NewCall(funcName, eh.NewIdent(CELRequestVarName), args[0]), nil
 		}
 		return nil, eh.NewError(args[0].ID(), "matcher argument must be a string literal")
 	}
@@ -572,7 +579,7 @@ func celMatcherJSONMacroExpander(funcName string) parser.MacroExpander {
 					return nil, eh.NewError(entry.AsMapEntry().Value().ID(), "matcher map values must be string or list literals")
 				}
 			}
-			return eh.NewCall(funcName, eh.NewIdent("request"), arg), nil
+			return eh.NewCall(funcName, eh.NewIdent(CELRequestVarName), arg), nil
 		case ast.UnspecifiedExprKind, ast.CallKind, ast.ComprehensionKind, ast.IdentKind, ast.ListKind, ast.LiteralKind, ast.SelectKind:
 			// appeasing the linter :)
 		}
@@ -646,7 +653,7 @@ func isCELCaddyPlaceholderCall(e ast.Expr) bool {
 	switch e.Kind() {
 	case ast.CallKind:
 		call := e.AsCall()
-		if call.FunctionName() == "caddyPlaceholder" {
+		if call.FunctionName() == CELPlaceholderFuncName {
 			return true
 		}
 	case ast.UnspecifiedExprKind, ast.ComprehensionKind, ast.IdentKind, ast.ListKind, ast.LiteralKind, ast.MapKind, ast.SelectKind, ast.StructKind:
@@ -701,8 +708,15 @@ func isCELStringListLiteral(e ast.Expr) bool {
 // expressions with a proper CEL function call; this is
 // just for syntactic sugar.
 var (
-	placeholderRegexp    = regexp.MustCompile(`{([a-zA-Z][\w.-]+)}`)
-	placeholderExpansion = `caddyPlaceholder(request, "${1}")`
+	// The placeholder may not be preceded by a backslash; the expansion
+	// will include the preceding character if it is not a backslash.
+	placeholderRegexp    = regexp.MustCompile(`([^\\]|^){([a-zA-Z][\w.-]+)}`)
+	placeholderExpansion = `${1}ph(req, "${2}")`
+
+	// As a second pass, we need to strip the escape character in front of
+	// the placeholder, if it exists.
+	escapedPlaceholderRegexp    = regexp.MustCompile(`\\{([a-zA-Z][\w.-]+)}`)
+	escapedPlaceholderExpansion = `{${1}}`
 
 	CELTypeJSON = cel.MapType(cel.StringType, cel.DynType)
 )
@@ -710,7 +724,10 @@ var (
 var httpRequestObjectType = cel.ObjectType("http.Request")
 
 // The name of the CEL function which accesses Replacer values.
-const placeholderFuncName = "caddyPlaceholder"
+const CELPlaceholderFuncName = "ph"
+
+// The name of the CEL request variable.
+const CELRequestVarName = "req"
 
 const MatcherNameCtxKey = "matcher_name"
 
diff --git a/modules/caddyhttp/celmatcher_test.go b/modules/caddyhttp/celmatcher_test.go
index 25fdcf45e..26491b7ca 100644
--- a/modules/caddyhttp/celmatcher_test.go
+++ b/modules/caddyhttp/celmatcher_test.go
@@ -70,13 +70,36 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			wantResult: true,
 		},
 		{
-			name: "header error (MatchHeader)",
+			name: "header matches an escaped placeholder value (MatchHeader)",
 			expression: &MatchExpression{
-				Expr: `header('foo')`,
+				Expr: `header({'Field': '\\\{foobar}'})`,
 			},
 			urlTarget:  "https://example.com/foo",
-			httpHeader: &http.Header{"Field": []string{"foo", "bar"}},
-			wantErr:    true,
+			httpHeader: &http.Header{"Field": []string{"{foobar}"}},
+			wantResult: true,
+		},
+		{
+			name: "header matches an placeholder replaced during the header matcher (MatchHeader)",
+			expression: &MatchExpression{
+				Expr: `header({'Field': '\{http.request.uri.path}'})`,
+			},
+			urlTarget:  "https://example.com/foo",
+			httpHeader: &http.Header{"Field": []string{"/foo"}},
+			wantResult: true,
+		},
+		{
+			name: "header error, invalid escape sequence (MatchHeader)",
+			expression: &MatchExpression{
+				Expr: `header({'Field': '\\{foobar}'})`,
+			},
+			wantErr: true,
+		},
+		{
+			name: "header error, needs to be JSON syntax with field as key (MatchHeader)",
+			expression: &MatchExpression{
+				Expr: `header('foo')`,
+			},
+			wantErr: true,
 		},
 		{
 			name: "header_regexp matches (MatchHeaderRE)",
@@ -110,9 +133,7 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			expression: &MatchExpression{
 				Expr: `header_regexp('foo')`,
 			},
-			urlTarget:  "https://example.com/foo",
-			httpHeader: &http.Header{"Field": []string{"foo", "bar"}},
-			wantErr:    true,
+			wantErr: true,
 		},
 		{
 			name: "host matches localhost (MatchHost)",
@@ -143,8 +164,7 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			expression: &MatchExpression{
 				Expr: `host(80)`,
 			},
-			urlTarget: "http://localhost:80",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "method does not match (MatchMethod)",
@@ -169,9 +189,7 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			expression: &MatchExpression{
 				Expr: `method()`,
 			},
-			urlTarget:  "https://foo.example.com",
-			httpMethod: "PUT",
-			wantErr:    true,
+			wantErr: true,
 		},
 		{
 			name: "path matches substring (MatchPath)",
@@ -266,24 +284,21 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			expression: &MatchExpression{
 				Expr: `protocol()`,
 			},
-			urlTarget: "https://example.com",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "protocol invocation error too many args (MatchProtocol)",
 			expression: &MatchExpression{
 				Expr: `protocol('grpc', 'https')`,
 			},
-			urlTarget: "https://example.com",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "protocol invocation error wrong arg type (MatchProtocol)",
 			expression: &MatchExpression{
 				Expr: `protocol(true)`,
 			},
-			urlTarget: "https://example.com",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "query does not match against a specific value (MatchQuery)",
@@ -330,40 +345,35 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			expression: &MatchExpression{
 				Expr: `query({1: "1"})`,
 			},
-			urlTarget: "https://example.com/foo",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "query error typed struct instead of map (MatchQuery)",
 			expression: &MatchExpression{
 				Expr: `query(Message{field: "1"})`,
 			},
-			urlTarget: "https://example.com/foo",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "query error bad map value type (MatchQuery)",
 			expression: &MatchExpression{
 				Expr: `query({"debug": 1})`,
 			},
-			urlTarget: "https://example.com/foo/?debug=1",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "query error no args (MatchQuery)",
 			expression: &MatchExpression{
 				Expr: `query()`,
 			},
-			urlTarget: "https://example.com/foo/?debug=1",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "remote_ip error no args (MatchRemoteIP)",
 			expression: &MatchExpression{
 				Expr: `remote_ip()`,
 			},
-			urlTarget: "https://example.com/foo",
-			wantErr:   true,
+			wantErr: true,
 		},
 		{
 			name: "remote_ip single IP match (MatchRemoteIP)",
@@ -373,6 +383,67 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			urlTarget:  "https://example.com/foo",
 			wantResult: true,
 		},
+		{
+			name: "vars value (VarsMatcher)",
+			expression: &MatchExpression{
+				Expr: `vars({'foo': 'bar'})`,
+			},
+			urlTarget:  "https://example.com/foo",
+			wantResult: true,
+		},
+		{
+			name: "vars matches placeholder, needs escape (VarsMatcher)",
+			expression: &MatchExpression{
+				Expr: `vars({'\{http.request.uri.path}': '/foo'})`,
+			},
+			urlTarget:  "https://example.com/foo",
+			wantResult: true,
+		},
+		{
+			name: "vars error wrong syntax (VarsMatcher)",
+			expression: &MatchExpression{
+				Expr: `vars('foo', 'bar')`,
+			},
+			wantErr: true,
+		},
+		{
+			name: "vars error no args (VarsMatcher)",
+			expression: &MatchExpression{
+				Expr: `vars()`,
+			},
+			wantErr: true,
+		},
+		{
+			name: "vars_regexp value (MatchVarsRE)",
+			expression: &MatchExpression{
+				Expr: `vars_regexp('foo', 'ba?r')`,
+			},
+			urlTarget:  "https://example.com/foo",
+			wantResult: true,
+		},
+		{
+			name: "vars_regexp value with name (MatchVarsRE)",
+			expression: &MatchExpression{
+				Expr: `vars_regexp('name', 'foo', 'ba?r')`,
+			},
+			urlTarget:  "https://example.com/foo",
+			wantResult: true,
+		},
+		{
+			name: "vars_regexp matches placeholder, needs escape (MatchVarsRE)",
+			expression: &MatchExpression{
+				Expr: `vars_regexp('\{http.request.uri.path}', '/fo?o')`,
+			},
+			urlTarget:  "https://example.com/foo",
+			wantResult: true,
+		},
+		{
+			name: "vars_regexp error no args (MatchVarsRE)",
+			expression: &MatchExpression{
+				Expr: `vars_regexp()`,
+			},
+			wantErr: true,
+		},
 	}
 )
 
@@ -396,6 +467,9 @@ func TestMatchExpressionMatch(t *testing.T) {
 			}
 			repl := caddy.NewReplacer()
 			ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)
+			ctx = context.WithValue(ctx, VarsCtxKey, map[string]any{
+				"foo": "bar",
+			})
 			req = req.WithContext(ctx)
 			addHTTPVarsToReplacer(repl, req, httptest.NewRecorder())
 
@@ -436,6 +510,9 @@ func BenchmarkMatchExpressionMatch(b *testing.B) {
 			}
 			repl := caddy.NewReplacer()
 			ctx := context.WithValue(req.Context(), caddy.ReplacerCtxKey, repl)
+			ctx = context.WithValue(ctx, VarsCtxKey, map[string]any{
+				"foo": "bar",
+			})
 			req = req.WithContext(ctx)
 			addHTTPVarsToReplacer(repl, req, httptest.NewRecorder())
 			if tc.clientCertificate != nil {
diff --git a/modules/caddyhttp/fileserver/matcher.go b/modules/caddyhttp/fileserver/matcher.go
index 6ab2180ad..71de1db29 100644
--- a/modules/caddyhttp/fileserver/matcher.go
+++ b/modules/caddyhttp/fileserver/matcher.go
@@ -225,7 +225,7 @@ func celFileMatcherMacroExpander() parser.MacroExpander {
 	return func(eh parser.ExprHelper, target ast.Expr, args []ast.Expr) (ast.Expr, *common.Error) {
 		if len(args) == 0 {
 			return eh.NewCall("file",
-				eh.NewIdent("request"),
+				eh.NewIdent(caddyhttp.CELRequestVarName),
 				eh.NewMap(),
 			), nil
 		}
@@ -233,7 +233,7 @@ func celFileMatcherMacroExpander() parser.MacroExpander {
 			arg := args[0]
 			if isCELStringLiteral(arg) || isCELCaddyPlaceholderCall(arg) {
 				return eh.NewCall("file",
-					eh.NewIdent("request"),
+					eh.NewIdent(caddyhttp.CELRequestVarName),
 					eh.NewMap(eh.NewMapEntry(
 						eh.NewLiteral(types.String("try_files")),
 						eh.NewList(arg),
@@ -242,7 +242,7 @@ func celFileMatcherMacroExpander() parser.MacroExpander {
 				), nil
 			}
 			if isCELTryFilesLiteral(arg) {
-				return eh.NewCall("file", eh.NewIdent("request"), arg), nil
+				return eh.NewCall("file", eh.NewIdent(caddyhttp.CELRequestVarName), arg), nil
 			}
 			return nil, &common.Error{
 				Location: eh.OffsetLocation(arg.ID()),
@@ -259,7 +259,7 @@ func celFileMatcherMacroExpander() parser.MacroExpander {
 			}
 		}
 		return eh.NewCall("file",
-			eh.NewIdent("request"),
+			eh.NewIdent(caddyhttp.CELRequestVarName),
 			eh.NewMap(eh.NewMapEntry(
 				eh.NewLiteral(types.String("try_files")),
 				eh.NewList(args...),
@@ -634,7 +634,7 @@ func isCELCaddyPlaceholderCall(e ast.Expr) bool {
 	switch e.Kind() {
 	case ast.CallKind:
 		call := e.AsCall()
-		if call.FunctionName() == "caddyPlaceholder" {
+		if call.FunctionName() == caddyhttp.CELPlaceholderFuncName {
 			return true
 		}
 	case ast.UnspecifiedExprKind, ast.ComprehensionKind, ast.IdentKind, ast.ListKind, ast.LiteralKind, ast.MapKind, ast.SelectKind, ast.StructKind:
diff --git a/modules/caddyhttp/matchers.go b/modules/caddyhttp/matchers.go
index a0bc6d63a..93a36237b 100644
--- a/modules/caddyhttp/matchers.go
+++ b/modules/caddyhttp/matchers.go
@@ -1562,8 +1562,8 @@ var (
 	_ CELLibraryProducer = (*MatchHeader)(nil)
 	_ CELLibraryProducer = (*MatchHeaderRE)(nil)
 	_ CELLibraryProducer = (*MatchProtocol)(nil)
-	// _ CELLibraryProducer = (*VarsMatcher)(nil)
-	// _ CELLibraryProducer = (*MatchVarsRE)(nil)
+	_ CELLibraryProducer = (*VarsMatcher)(nil)
+	_ CELLibraryProducer = (*MatchVarsRE)(nil)
 
 	_ json.Marshaler   = (*MatchNot)(nil)
 	_ json.Unmarshaler = (*MatchNot)(nil)
diff --git a/modules/caddyhttp/templates/templates.go b/modules/caddyhttp/templates/templates.go
index 0eba4870f..eb6488659 100644
--- a/modules/caddyhttp/templates/templates.go
+++ b/modules/caddyhttp/templates/templates.go
@@ -81,6 +81,12 @@ func init() {
 // {{placeholder "http.error.status_code"}}
 // ```
 //
+// As a shortcut, `ph` is an alias for `placeholder`.
+//
+// ```
+// {{ph "http.request.method"}}
+// ```
+//
 // ##### `.Host`
 //
 // Returns the hostname portion (no port) of the Host header of the HTTP request.
diff --git a/modules/caddyhttp/templates/tplcontext.go b/modules/caddyhttp/templates/tplcontext.go
index 2324586be..1b1020f1b 100644
--- a/modules/caddyhttp/templates/tplcontext.go
+++ b/modules/caddyhttp/templates/tplcontext.go
@@ -88,6 +88,7 @@ func (c *TemplateContext) NewTemplate(tplName string) *template.Template {
 		"fileStat":         c.funcFileStat,
 		"env":              c.funcEnv,
 		"placeholder":      c.funcPlaceholder,
+		"ph":               c.funcPlaceholder, // shortcut
 		"fileExists":       c.funcFileExists,
 		"httpError":        c.funcHTTPError,
 		"humanize":         c.funcHumanize,
diff --git a/modules/caddyhttp/vars.go b/modules/caddyhttp/vars.go
index 9e86dd716..77e06e3cb 100644
--- a/modules/caddyhttp/vars.go
+++ b/modules/caddyhttp/vars.go
@@ -18,8 +18,12 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"reflect"
 	"strings"
 
+	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/common/types/ref"
+
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
 )
@@ -203,6 +207,28 @@ func (m VarsMatcher) Match(r *http.Request) bool {
 	return false
 }
 
+// CELLibrary produces options that expose this matcher for use in CEL
+// expression matchers.
+//
+// Example:
+//
+//	expression vars({'{magic_number}': ['3', '5']})
+//	expression vars({'{foo}': 'single_value'})
+func (VarsMatcher) CELLibrary(_ caddy.Context) (cel.Library, error) {
+	return CELMatcherImpl(
+		"vars",
+		"vars_matcher_request_map",
+		[]*cel.Type{CELTypeJSON},
+		func(data ref.Val) (RequestMatcher, error) {
+			mapStrListStr, err := CELValueToMapStrList(data)
+			if err != nil {
+				return nil, err
+			}
+			return VarsMatcher(mapStrListStr), nil
+		},
+	)
+}
+
 // MatchVarsRE matches the value of the context variables by a given regular expression.
 //
 // Upon a match, it adds placeholders to the request: `{http.regexp.name.capture_group}`
@@ -302,6 +328,69 @@ func (m MatchVarsRE) Match(r *http.Request) bool {
 	return false
 }
 
+// CELLibrary produces options that expose this matcher for use in CEL
+// expression matchers.
+//
+// Example:
+//
+//	expression vars_regexp('foo', '{magic_number}', '[0-9]+')
+//	expression vars_regexp('{magic_number}', '[0-9]+')
+func (MatchVarsRE) CELLibrary(ctx caddy.Context) (cel.Library, error) {
+	unnamedPattern, err := CELMatcherImpl(
+		"vars_regexp",
+		"vars_regexp_request_string_string",
+		[]*cel.Type{cel.StringType, cel.StringType},
+		func(data ref.Val) (RequestMatcher, error) {
+			refStringList := reflect.TypeOf([]string{})
+			params, err := data.ConvertToNative(refStringList)
+			if err != nil {
+				return nil, err
+			}
+			strParams := params.([]string)
+			matcher := MatchVarsRE{}
+			matcher[strParams[0]] = &MatchRegexp{
+				Pattern: strParams[1],
+				Name:    ctx.Value(MatcherNameCtxKey).(string),
+			}
+			err = matcher.Provision(ctx)
+			return matcher, err
+		},
+	)
+	if err != nil {
+		return nil, err
+	}
+	namedPattern, err := CELMatcherImpl(
+		"vars_regexp",
+		"vars_regexp_request_string_string_string",
+		[]*cel.Type{cel.StringType, cel.StringType, cel.StringType},
+		func(data ref.Val) (RequestMatcher, error) {
+			refStringList := reflect.TypeOf([]string{})
+			params, err := data.ConvertToNative(refStringList)
+			if err != nil {
+				return nil, err
+			}
+			strParams := params.([]string)
+			name := strParams[0]
+			if name == "" {
+				name = ctx.Value(MatcherNameCtxKey).(string)
+			}
+			matcher := MatchVarsRE{}
+			matcher[strParams[1]] = &MatchRegexp{
+				Pattern: strParams[2],
+				Name:    name,
+			}
+			err = matcher.Provision(ctx)
+			return matcher, err
+		},
+	)
+	if err != nil {
+		return nil, err
+	}
+	envOpts := append(unnamedPattern.CompileOptions(), namedPattern.CompileOptions()...)
+	prgOpts := append(unnamedPattern.ProgramOptions(), namedPattern.ProgramOptions()...)
+	return NewMatcherCELLibrary(envOpts, prgOpts), nil
+}
+
 // Validate validates m's regular expressions.
 func (m MatchVarsRE) Validate() error {
 	for _, rm := range m {