diff --git a/docs/expressions.md b/docs/expressions.md
index 14b6e44..8c10d83 100644
--- a/docs/expressions.md
+++ b/docs/expressions.md
@@ -140,7 +140,7 @@ On a CEL variable named `subject` of value:
 
 ```json
 [
-  "one", null, "two",
+  "one", null, "two"
 ]
 ```
 
@@ -159,3 +159,17 @@ On a CEL variable named `subject` of value:
 - `trimPrefix(subject, "something:")` => `group:engineering@example.com`
 - `trimPrefix(subject, "group:")` => `engineering@example.com`
 
+### `replace`
+
+Performs a RegEx replace on a string using [RE2 syntax](https://github.com/google/re2/wiki/Syntax).
+If there are no pattern matches, the input string will be returned. `replace` supports group references (`$1`).
+
+On a CEL variable named `subject` of value:
+
+```json
+"group:engineering@example.com"
+```
+
+- `replace(subject, "group:([[:alpha:]]+)@.+$", "$1")` => `engineering`
+- `replace(subject, "@example\\.com", "")` => `group:engineering`
+- `replace(subject, ".+@test.example.com"` => `group:engineering@example.com` (no match)
diff --git a/expr/functions.go b/expr/functions.go
index d5e0251..2635df6 100644
--- a/expr/functions.go
+++ b/expr/functions.go
@@ -2,6 +2,7 @@ package expr
 
 import (
 	"reflect"
+	"regexp"
 	"strings"
 
 	"github.com/google/cel-go/cel"
@@ -28,6 +29,7 @@ func (*stdlib) CompileOptions() []cel.EnvOption {
 		Coalesce(),
 		First(),
 		TrimPrefix(),
+		Replace(),
 	}
 }
 
@@ -128,3 +130,25 @@ func TrimPrefix() cel.EnvOption {
 		),
 	)
 }
+
+// Replace removes the given string from the front of the input.
+func Replace() cel.EnvOption {
+	binding := func(vals ...ref.Val) ref.Val {
+		input, pattern, replacement := vals[0], vals[1], vals[2]
+		regex, err := regexp.Compile(pattern.Value().(string))
+		if err != nil {
+			return types.WrapErr(err)
+		}
+
+		return types.String(regex.ReplaceAllString(input.Value().(string), replacement.Value().(string)))
+	}
+
+	return cel.Function("replace",
+		cel.Overload("replace_string_string_string",
+			[]*cel.Type{cel.StringType, cel.StringType, cel.StringType},
+			cel.StringType,
+			cel.FunctionBinding(binding),
+			//cel.BinaryBinding(binding),
+		),
+	)
+}
diff --git a/expr/functions_test.go b/expr/functions_test.go
index 1fd6a5d..d00a1ad 100644
--- a/expr/functions_test.go
+++ b/expr/functions_test.go
@@ -6,7 +6,6 @@ import (
 	"github.com/google/cel-go/cel"
 	"github.com/google/cel-go/common/types"
 	"github.com/google/cel-go/common/types/ref"
-
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 )
@@ -112,4 +111,38 @@ var _ = Describe("Functions", func() {
 			})
 		})
 	})
+
+	Describe("Replace", func() {
+		BeforeEach(func() {
+			src = "replace(value, r'^https://([0-9A-Za-z_\\-]+)\\.example\\.com.*$', '$1')"
+		})
+
+		When("the input is a matching string", func() {
+			It("Returns the replacement", func() {
+				out, _, err := prg.Eval(map[string]any{
+					"value": "https://some-slug.example.com/test",
+				})
+				Expect(err).NotTo(HaveOccurred())
+
+				result, err := out.ConvertToNative(reflect.TypeOf(""))
+				Expect(err).NotTo(HaveOccurred())
+
+				Expect(result).To(Equal("some-slug"))
+			})
+		})
+
+		When("the input has no matches", func() {
+			It("returns the source string", func() {
+				out, _, err := prg.Eval(map[string]any{
+					"value": "https://some-slug.incident.io/test",
+				})
+				Expect(err).NotTo(HaveOccurred())
+
+				result, err := out.ConvertToNative(reflect.TypeOf(""))
+				Expect(err).NotTo(HaveOccurred())
+
+				Expect(result).To(Equal("https://some-slug.incident.io/test"))
+			})
+		})
+	})
 })
diff --git a/go.mod b/go.mod
index 7440701..788a0e8 100644
--- a/go.mod
+++ b/go.mod
@@ -22,8 +22,8 @@ require (
 	github.com/hashicorp/go-retryablehttp v0.7.2
 	github.com/machinebox/graphql v0.2.2
 	github.com/manifoldco/promptui v0.9.0
-	github.com/onsi/ginkgo/v2 v2.9.2
-	github.com/onsi/gomega v1.27.6
+	github.com/onsi/ginkgo/v2 v2.11.0
+	github.com/onsi/gomega v1.27.8
 	github.com/pkg/errors v0.9.1
 	github.com/rodaine/table v1.1.0
 	github.com/samber/lo v1.38.1
@@ -32,7 +32,7 @@ require (
 	github.com/yargevad/filepathx v1.0.0
 	github.com/zyedidia/highlight v0.0.0-20200217010119-291680feaca1
 	golang.org/x/oauth2 v0.8.0
-	golang.org/x/sync v0.1.0
+	golang.org/x/sync v0.2.0
 	gopkg.in/guregu/null.v3 v3.5.0
 	gopkg.in/yaml.v2 v2.4.0
 )
@@ -47,7 +47,7 @@ require (
 	github.com/cloudflare/circl v1.1.0 // indirect
 	github.com/getkin/kin-openapi v0.107.0 // indirect
 	github.com/go-logfmt/logfmt v0.5.1 // indirect
-	github.com/go-logr/logr v1.2.3 // indirect
+	github.com/go-logr/logr v1.2.4 // indirect
 	github.com/go-openapi/jsonpointer v0.19.5 // indirect
 	github.com/go-openapi/swag v0.21.1 // indirect
 	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
@@ -72,12 +72,12 @@ require (
 	github.com/xhit/go-str2duration/v2 v2.1.0 // indirect
 	golang.org/x/crypto v0.7.0 // indirect
 	golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e // indirect
-	golang.org/x/mod v0.9.0 // indirect
+	golang.org/x/mod v0.10.0 // indirect
 	golang.org/x/net v0.10.0 // indirect
-	golang.org/x/sys v0.8.0 // indirect
+	golang.org/x/sys v0.9.0 // indirect
 	golang.org/x/term v0.8.0 // indirect
 	golang.org/x/text v0.9.0 // indirect
-	golang.org/x/tools v0.7.0 // indirect
+	golang.org/x/tools v0.9.3 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto v0.0.0-20221207170731-23e4bf6bdc37 // indirect
 	google.golang.org/protobuf v1.28.1 // indirect
diff --git a/go.sum b/go.sum
index ea3b54a..1a0b5ce 100644
--- a/go.sum
+++ b/go.sum
@@ -43,6 +43,8 @@ github.com/go-logfmt/logfmt v0.5.1 h1:otpy5pqBCBZ1ng9RQ0dPu4PN7ba75Y/aA+UpowDyNV
 github.com/go-logfmt/logfmt v0.5.1/go.mod h1:WYhtIu8zTZfxdn5+rREduYbwxfcBr/Vr6KEVveWlfTs=
 github.com/go-logr/logr v1.2.3 h1:2DntVwHkVopvECVRSlL5PSo9eG+cAkDCuckLubN+rq0=
 github.com/go-logr/logr v1.2.3/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
+github.com/go-logr/logr v1.2.4 h1:g01GSCwiDw2xSZfjJ2/T9M+S6pFdcNtFYsp+Y43HYDQ=
+github.com/go-logr/logr v1.2.4/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-openapi/jsonpointer v0.19.5 h1:gZr+CIYByUqjcgeLXnQu2gHYQC9o73G2XUeOFYEICuY=
 github.com/go-openapi/jsonpointer v0.19.5/go.mod h1:Pl9vOtqEWErmShwVjC8pYs9cog34VGT37dQOVbmoatg=
 github.com/go-openapi/swag v0.19.5/go.mod h1:POnQmlKehdgb5mhVOsnJFsivZCEZ/vjK9gh66Z9tfKk=
@@ -131,8 +133,12 @@ github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e h1:fD57ERR4JtEqsWb
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/onsi/ginkgo/v2 v2.9.2 h1:BA2GMJOtfGAfagzYtrAlufIP0lq6QERkFmHLMLPwFSU=
 github.com/onsi/ginkgo/v2 v2.9.2/go.mod h1:WHcJJG2dIlcCqVfBAwUCrJxSPFb6v4azBwgxeMeDuts=
+github.com/onsi/ginkgo/v2 v2.11.0 h1:WgqUCUt/lT6yXoQ8Wef0fsNn5cAuMK7+KT9UFRz2tcU=
+github.com/onsi/ginkgo/v2 v2.11.0/go.mod h1:ZhrRA5XmEE3x3rhlzamx/JJvujdZoJ2uvgI7kR0iZvM=
 github.com/onsi/gomega v1.27.6 h1:ENqfyGeS5AX/rlXDd/ETokDz93u0YufY1Pgxuy/PvWE=
 github.com/onsi/gomega v1.27.6/go.mod h1:PIQNjfQwkP3aQAH7lf7j87O/5FiNr+ZR8+ipb+qQlhg=
+github.com/onsi/gomega v1.27.8 h1:gegWiwZjBsf2DgiSbf5hpokZ98JVDMcWkUiigk6/KXc=
+github.com/onsi/gomega v1.27.8/go.mod h1:2J8vzI/s+2shY9XHRApDkdgPo1TKT7P2u6fXeJKFnNQ=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -182,6 +188,7 @@ golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e h1:+WEEuIdZHnUeJJmEUjyYC2gfU
 golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e/go.mod h1:Kr81I6Kryrl9sr8s2FK3vxD90NdsKWRuOIl2O4CvYbA=
 golang.org/x/mod v0.9.0 h1:KENHtAZL2y3NLMYZeHY9DW8HW8V+kQyJsY/V9JlKvCs=
 golang.org/x/mod v0.9.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/mod v0.10.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
@@ -190,6 +197,8 @@ golang.org/x/oauth2 v0.8.0 h1:6dkIjl3j3LtZ/O3sTgZTMsLKSftL/B8Zgq4huOIIUu8=
 golang.org/x/oauth2 v0.8.0/go.mod h1:yr7u4HXZRm1R1kBWqr/xKNqewf0plRYoB7sla+BCIXE=
 golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.2.0 h1:PUR+T4wwASmuSTYdKjYHI5TD22Wy5ogLU5qZCOLxBrI=
+golang.org/x/sync v0.2.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20181122145206-62eef0e2fa9b/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -205,6 +214,8 @@ golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
 golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.9.0 h1:KS/R3tvhPqvJvwcKfnBHJwwthS11LRhmM5D59eEXa0s=
+golang.org/x/sys v0.9.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.6.0/go.mod h1:m6U89DPEgQRMq3DNkDClhWw02AUbt2daBVO4cn4Hv9U=
 golang.org/x/term v0.8.0 h1:n5xxQn2i3PC0yLAbjTpNT85q/Kgzcr2gIoX9OrJUols=
@@ -217,6 +228,8 @@ golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.7.0 h1:W4OVu8VVOaIO0yzWMNdepAulS7YfoS3Zabrm8DOXXU4=
 golang.org/x/tools v0.7.0/go.mod h1:4pg6aUX35JBAogB10C9AtvVL+qowtN4pT3CGSQex14s=
+golang.org/x/tools v0.9.3 h1:Gn1I8+64MsuTb/HpH+LmQtNas23LhUVr3rYZ0eKuaMM=
+golang.org/x/tools v0.9.3/go.mod h1:owI94Op576fPu3cIGQeHs3joujW/2Oc6MtlxbF5dfNc=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.6.7 h1:FZR1q0exgwxzPzp/aF+VccGrSfxfPpkBqjIIEq3ru6c=
 google.golang.org/appengine v1.6.7/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=