diff --git a/bake/hcl_test.go b/bake/hcl_test.go
index 31abc43e..f33722c7 100644
--- a/bake/hcl_test.go
+++ b/bake/hcl_test.go
@@ -1445,6 +1445,39 @@ func TestVarUnsupportedType(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestHCLIndexOfFunc(t *testing.T) {
+	dt := []byte(`
+		variable "APP_VERSIONS" {
+		  default = [
+			"1.42.4",
+			"1.42.3"
+		  ]
+		}
+		target "default" {
+			args = {
+				APP_VERSION = app_version
+			}
+			matrix = {
+				app_version = APP_VERSIONS
+			}
+			name="app-${replace(app_version, ".", "-")}"
+			tags = [
+				"app:${app_version}",
+				indexof(APP_VERSIONS, app_version) == 0 ? "app:latest" : "",
+			]
+		}
+		`)
+
+	c, err := ParseFile(dt, "docker-bake.hcl")
+	require.NoError(t, err)
+
+	require.Equal(t, 2, len(c.Targets))
+	require.Equal(t, "app-1-42-4", c.Targets[0].Name)
+	require.Equal(t, "app:latest", c.Targets[0].Tags[1])
+	require.Equal(t, "app-1-42-3", c.Targets[1].Name)
+	require.Empty(t, c.Targets[1].Tags[1])
+}
+
 func ptrstr(s interface{}) *string {
 	var n *string
 	if reflect.ValueOf(s).Kind() == reflect.String {
diff --git a/bake/hclparser/stdlib.go b/bake/hclparser/stdlib.go
index 660fef14..e0cd9b5f 100644
--- a/bake/hclparser/stdlib.go
+++ b/bake/hclparser/stdlib.go
@@ -9,6 +9,7 @@ import (
 	"github.com/hashicorp/go-cty-funcs/uuid"
 	"github.com/hashicorp/hcl/v2/ext/tryfunc"
 	"github.com/hashicorp/hcl/v2/ext/typeexpr"
+	"github.com/pkg/errors"
 	"github.com/zclconf/go-cty/cty"
 	"github.com/zclconf/go-cty/cty/function"
 	"github.com/zclconf/go-cty/cty/function/stdlib"
@@ -52,6 +53,7 @@ var stdlibFunctions = map[string]function.Function{
 	"hasindex":               stdlib.HasIndexFunc,
 	"indent":                 stdlib.IndentFunc,
 	"index":                  stdlib.IndexFunc,
+	"indexof":                indexOfFunc,
 	"int":                    stdlib.IntFunc,
 	"join":                   stdlib.JoinFunc,
 	"jsondecode":             stdlib.JSONDecodeFunc,
@@ -115,6 +117,51 @@ var stdlibFunctions = map[string]function.Function{
 	"zipmap":                 stdlib.ZipmapFunc,
 }
 
+// indexOfFunc constructs a function that finds the element index for a given
+// value in a list.
+var indexOfFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "list",
+			Type: cty.DynamicPseudoType,
+		},
+		{
+			Name: "value",
+			Type: cty.DynamicPseudoType,
+		},
+	},
+	Type: function.StaticReturnType(cty.Number),
+	Impl: func(args []cty.Value, retType cty.Type) (ret cty.Value, err error) {
+		if !(args[0].Type().IsListType() || args[0].Type().IsTupleType()) {
+			return cty.NilVal, errors.New("argument must be a list or tuple")
+		}
+
+		if !args[0].IsKnown() {
+			return cty.UnknownVal(cty.Number), nil
+		}
+
+		if args[0].LengthInt() == 0 { // Easy path
+			return cty.NilVal, errors.New("cannot search an empty list")
+		}
+
+		for it := args[0].ElementIterator(); it.Next(); {
+			i, v := it.Element()
+			eq, err := stdlib.Equal(v, args[1])
+			if err != nil {
+				return cty.NilVal, err
+			}
+			if !eq.IsKnown() {
+				return cty.UnknownVal(cty.Number), nil
+			}
+			if eq.True() {
+				return i, nil
+			}
+		}
+		return cty.NilVal, errors.New("item not found")
+
+	},
+})
+
 // timestampFunc constructs a function that returns a string representation of the current date and time.
 //
 // This function was imported from terraform's datetime utilities.
diff --git a/bake/hclparser/stdlib_test.go b/bake/hclparser/stdlib_test.go
new file mode 100644
index 00000000..df2336ce
--- /dev/null
+++ b/bake/hclparser/stdlib_test.go
@@ -0,0 +1,49 @@
+package hclparser
+
+import (
+	"testing"
+
+	"github.com/zclconf/go-cty/cty"
+)
+
+func TestIndexOf(t *testing.T) {
+	type testCase struct {
+		input   cty.Value
+		key     cty.Value
+		want    cty.Value
+		wantErr bool
+	}
+	tests := map[string]testCase{
+		"index 0": {
+			input: cty.TupleVal([]cty.Value{cty.StringVal("one"), cty.NumberIntVal(2.0), cty.NumberIntVal(3), cty.StringVal("four")}),
+			key:   cty.StringVal("one"),
+			want:  cty.NumberIntVal(0),
+		},
+		"index 3": {
+			input: cty.TupleVal([]cty.Value{cty.StringVal("one"), cty.NumberIntVal(2.0), cty.NumberIntVal(3), cty.StringVal("four")}),
+			key:   cty.StringVal("four"),
+			want:  cty.NumberIntVal(3),
+		},
+		"index -1": {
+			input:   cty.TupleVal([]cty.Value{cty.StringVal("one"), cty.NumberIntVal(2.0), cty.NumberIntVal(3), cty.StringVal("four")}),
+			key:     cty.StringVal("3"),
+			wantErr: true,
+		},
+	}
+
+	for name, test := range tests {
+		name, test := name, test
+		t.Run(name, func(t *testing.T) {
+			got, err := indexOfFunc.Call([]cty.Value{test.input, test.key})
+			if err != nil {
+				if test.wantErr {
+					return
+				}
+				t.Fatalf("unexpected error: %s", err)
+			}
+			if !got.RawEquals(test.want) {
+				t.Errorf("wrong result\ngot:  %#v\nwant: %#v", got, test.want)
+			}
+		})
+	}
+}