diff --git a/go.mod b/go.mod
index 6a0e2e5..db8d094 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/blues/jsonata-go
 
-go 1.16
+go 1.23
diff --git a/v1.5.4/.claude/settings.local.json b/v1.5.4/.claude/settings.local.json
new file mode 100644
index 0000000..71100b4
--- /dev/null
+++ b/v1.5.4/.claude/settings.local.json
@@ -0,0 +1,10 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(ls)",
+      "Bash(go:*)",
+      "Bash(grep:*)"
+    ],
+    "deny": []
+  }
+}
\ No newline at end of file
diff --git a/callable.go b/v1.5.4/callable.go
similarity index 98%
rename from callable.go
rename to v1.5.4/callable.go
index ec08501..f681528 100644
--- a/callable.go
+++ b/v1.5.4/callable.go
@@ -11,9 +11,9 @@ import (
 	"regexp"
 	"strings"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 type callableName struct {
@@ -48,7 +48,7 @@ func newGoCallableParam(typ reflect.Type) goCallableParam {
 		t: typ,
 	}
 
-	isOpt := reflect.PtrTo(typ).Implements(jtypes.TypeOptional)
+	isOpt := reflect.PointerTo(typ).Implements(jtypes.TypeOptional)
 	if isOpt {
 		o := reflect.New(typ).Interface().(jtypes.Optional)
 		p := newGoCallableParam(o.Type())
@@ -294,7 +294,7 @@ func (c *goCallable) validateArgTypes(argv []reflect.Value) ([]reflect.Value, er
 		// This is fine for most types but we need to restore
 		// pointer type Callables.
 		if v.Kind() == reflect.Struct &&
-			reflect.PtrTo(v.Type()).Implements(jtypes.TypeCallable) {
+			reflect.PointerTo(v.Type()).Implements(jtypes.TypeCallable) {
 			if v.CanAddr() {
 				v = v.Addr()
 			}
diff --git a/callable_test.go b/v1.5.4/callable_test.go
similarity index 99%
rename from callable_test.go
rename to v1.5.4/callable_test.go
index 75062bc..1df5356 100644
--- a/callable_test.go
+++ b/v1.5.4/callable_test.go
@@ -13,8 +13,8 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 var (
diff --git a/doc.go b/v1.5.4/doc.go
similarity index 100%
rename from doc.go
rename to v1.5.4/doc.go
diff --git a/env.go b/v1.5.4/env.go
similarity index 98%
rename from env.go
rename to v1.5.4/env.go
index bbbefc5..2259d65 100644
--- a/env.go
+++ b/v1.5.4/env.go
@@ -11,9 +11,9 @@ import (
 	"strings"
 	"unicode/utf8"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 type environment struct {
diff --git a/error.go b/v1.5.4/error.go
similarity index 99%
rename from error.go
rename to v1.5.4/error.go
index f5d383c..8bd1bfc 100644
--- a/error.go
+++ b/v1.5.4/error.go
@@ -9,7 +9,7 @@ import (
 	"fmt"
 	"regexp"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // ErrUndefined is returned by the evaluation methods when
diff --git a/eval.go b/v1.5.4/eval.go
similarity index 99%
rename from eval.go
rename to v1.5.4/eval.go
index a66b561..a51cfea 100644
--- a/eval.go
+++ b/v1.5.4/eval.go
@@ -10,9 +10,9 @@ import (
 	"reflect"
 	"sort"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 var undefined reflect.Value
@@ -1343,7 +1343,7 @@ func (s sequence) Value() reflect.Value {
 
 var (
 	typeSequence    = reflect.TypeOf((*sequence)(nil)).Elem()
-	typeSequencePtr = reflect.PtrTo(typeSequence)
+	typeSequencePtr = reflect.PointerTo(typeSequence)
 )
 
 func asSequence(v reflect.Value) (*sequence, bool) {
diff --git a/eval_test.go b/v1.5.4/eval_test.go
similarity index 99%
rename from eval_test.go
rename to v1.5.4/eval_test.go
index 80c9378..5a4e4a4 100644
--- a/eval_test.go
+++ b/v1.5.4/eval_test.go
@@ -11,9 +11,9 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 type evalTestCase struct {
diff --git a/example_eval_test.go b/v1.5.4/example_eval_test.go
similarity index 94%
rename from example_eval_test.go
rename to v1.5.4/example_eval_test.go
index fd35592..8e8d015 100644
--- a/example_eval_test.go
+++ b/v1.5.4/example_eval_test.go
@@ -9,7 +9,7 @@ import (
 	"fmt"
 	"log"
 
-	jsonata "github.com/blues/jsonata-go"
+	jsonata "github.com/blues/jsonata-go/v1.5.4"
 )
 
 const jsonString = `
diff --git a/example_exts_test.go b/v1.5.4/example_exts_test.go
similarity index 65%
rename from example_exts_test.go
rename to v1.5.4/example_exts_test.go
index 2c02e18..1ffdee6 100644
--- a/example_exts_test.go
+++ b/v1.5.4/example_exts_test.go
@@ -8,8 +8,9 @@ import (
 	"fmt"
 	"log"
 	"strings"
+	"unicode"
 
-	jsonata "github.com/blues/jsonata-go"
+	jsonata "github.com/blues/jsonata-go/v1.5.4"
 )
 
 //
@@ -17,14 +18,29 @@ import (
 // custom functions.
 //
 
+// titleCase returns a copy of the string s with all Unicode letters that begin words
+// mapped to their Unicode title case.
+func titleCase(s string) string {
+	// Split the string into words
+	words := strings.Fields(s)
+	for i, word := range words {
+		runes := []rune(word)
+		if len(runes) > 0 {
+			runes[0] = unicode.ToTitle(runes[0])
+		}
+		words[i] = string(runes)
+	}
+	return strings.Join(words, " ")
+}
+
 // exts defines a function named "titlecase" which maps to
-// the standard library function strings.Title. Any function,
+// our custom titleCase function. Any function,
 // from the standard library or otherwise, can be used to
 // extend JSONata, as long as it returns either one or two
 // arguments (the second argument must be an error).
 var exts = map[string]jsonata.Extension{
 	"titlecase": {
-		Func: strings.Title,
+		Func: titleCase,
 	},
 }
 
diff --git a/jlib/aggregate.go b/v1.5.4/jlib/aggregate.go
similarity index 98%
rename from jlib/aggregate.go
rename to v1.5.4/jlib/aggregate.go
index 735ff82..4cfe368 100644
--- a/jlib/aggregate.go
+++ b/v1.5.4/jlib/aggregate.go
@@ -8,7 +8,7 @@ import (
 	"fmt"
 	"reflect"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // Sum returns the total of an array of numbers. If the array is
diff --git a/jlib/array.go b/v1.5.4/jlib/array.go
similarity index 99%
rename from jlib/array.go
rename to v1.5.4/jlib/array.go
index f16f711..f3089a6 100644
--- a/jlib/array.go
+++ b/v1.5.4/jlib/array.go
@@ -10,7 +10,7 @@ import (
 	"reflect"
 	"sort"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // Count (golint)
diff --git a/jlib/boolean.go b/v1.5.4/jlib/boolean.go
similarity index 94%
rename from jlib/boolean.go
rename to v1.5.4/jlib/boolean.go
index b4325f4..f39528e 100644
--- a/jlib/boolean.go
+++ b/v1.5.4/jlib/boolean.go
@@ -7,7 +7,7 @@ package jlib
 import (
 	"reflect"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // Boolean (golint)
diff --git a/jlib/date.go b/v1.5.4/jlib/date.go
similarity index 97%
rename from jlib/date.go
rename to v1.5.4/jlib/date.go
index 70a9a2c..f1a74ce 100644
--- a/jlib/date.go
+++ b/v1.5.4/jlib/date.go
@@ -10,8 +10,8 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/blues/jsonata-go/jlib/jxpath"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib/jxpath"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // 2006-01-02T15:04:05.000Z07:00
diff --git a/jlib/date_test.go b/v1.5.4/jlib/date_test.go
similarity index 96%
rename from jlib/date_test.go
rename to v1.5.4/jlib/date_test.go
index 7c42c62..dab8bba 100644
--- a/jlib/date_test.go
+++ b/v1.5.4/jlib/date_test.go
@@ -9,8 +9,8 @@ import (
 	"testing"
 	"time"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 func TestFromMillis(t *testing.T) {
diff --git a/jlib/error.go b/v1.5.4/jlib/error.go
similarity index 100%
rename from jlib/error.go
rename to v1.5.4/jlib/error.go
diff --git a/jlib/hof.go b/v1.5.4/jlib/hof.go
similarity index 98%
rename from jlib/hof.go
rename to v1.5.4/jlib/hof.go
index 6452a3b..e604b3b 100644
--- a/jlib/hof.go
+++ b/v1.5.4/jlib/hof.go
@@ -8,7 +8,7 @@ import (
 	"fmt"
 	"reflect"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // Map (golint)
diff --git a/jlib/jlib.go b/v1.5.4/jlib/jlib.go
similarity index 90%
rename from jlib/jlib.go
rename to v1.5.4/jlib/jlib.go
index 644a044..96eb319 100644
--- a/jlib/jlib.go
+++ b/v1.5.4/jlib/jlib.go
@@ -7,17 +7,13 @@ package jlib
 
 import (
 	"fmt"
-	"math/rand"
 	"reflect"
-	"time"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
-func init() {
-	// Seed random numbers for Random() and Shuffle().
-	rand.Seed(time.Now().UnixNano())
-}
+// Random numbers for Random() and Shuffle() functions are automatically seeded
+// in Go 1.20+ without needing to call rand.Seed
 
 var typeBool = reflect.TypeOf((*bool)(nil)).Elem()
 var typeCallable = reflect.TypeOf((*jtypes.Callable)(nil)).Elem()
diff --git a/jlib/jxpath/formatdate.go b/v1.5.4/jlib/jxpath/formatdate.go
similarity index 100%
rename from jlib/jxpath/formatdate.go
rename to v1.5.4/jlib/jxpath/formatdate.go
diff --git a/jlib/jxpath/formatdate_test.go b/v1.5.4/jlib/jxpath/formatdate_test.go
similarity index 100%
rename from jlib/jxpath/formatdate_test.go
rename to v1.5.4/jlib/jxpath/formatdate_test.go
diff --git a/jlib/jxpath/formatnumber.go b/v1.5.4/jlib/jxpath/formatnumber.go
similarity index 100%
rename from jlib/jxpath/formatnumber.go
rename to v1.5.4/jlib/jxpath/formatnumber.go
diff --git a/jlib/jxpath/formatnumber_test.go b/v1.5.4/jlib/jxpath/formatnumber_test.go
similarity index 100%
rename from jlib/jxpath/formatnumber_test.go
rename to v1.5.4/jlib/jxpath/formatnumber_test.go
diff --git a/jlib/jxpath/language.go b/v1.5.4/jlib/jxpath/language.go
similarity index 100%
rename from jlib/jxpath/language.go
rename to v1.5.4/jlib/jxpath/language.go
diff --git a/jlib/number.go b/v1.5.4/jlib/number.go
similarity index 97%
rename from jlib/number.go
rename to v1.5.4/jlib/number.go
index 8cb0e46..27f5e0c 100644
--- a/jlib/number.go
+++ b/v1.5.4/jlib/number.go
@@ -13,7 +13,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 var reNumber = regexp.MustCompile(`^-?(([0-9]+))(\.[0-9]+)?([Ee][-+]?[0-9]+)?$`)
@@ -116,7 +116,7 @@ func Random() float64 {
 // It does this by converting back and forth to strings to
 // avoid floating point rounding errors, e.g.
 //
-//     4.525 * math.Pow10(2) returns 452.50000000000006
+//	4.525 * math.Pow10(2) returns 452.50000000000006
 func multByPow10(x float64, n int) float64 {
 	if n == 0 || math.IsNaN(x) || math.IsInf(x, 0) {
 		return x
diff --git a/jlib/number_test.go b/v1.5.4/jlib/number_test.go
similarity index 96%
rename from jlib/number_test.go
rename to v1.5.4/jlib/number_test.go
index 51b422f..bf7a275 100644
--- a/jlib/number_test.go
+++ b/v1.5.4/jlib/number_test.go
@@ -8,8 +8,8 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 func TestRound(t *testing.T) {
diff --git a/jlib/object.go b/v1.5.4/jlib/object.go
similarity index 99%
rename from jlib/object.go
rename to v1.5.4/jlib/object.go
index ca43f8d..79fe20a 100644
--- a/jlib/object.go
+++ b/v1.5.4/jlib/object.go
@@ -8,7 +8,7 @@ import (
 	"fmt"
 	"reflect"
 
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // typeInterfaceMap is the reflect.Type for map[string]interface{}.
diff --git a/jlib/object_test.go b/v1.5.4/jlib/object_test.go
similarity index 99%
rename from jlib/object_test.go
rename to v1.5.4/jlib/object_test.go
index e2e8dc7..c40f5ce 100644
--- a/jlib/object_test.go
+++ b/v1.5.4/jlib/object_test.go
@@ -12,8 +12,8 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 type eachTest struct {
diff --git a/jlib/string.go b/v1.5.4/jlib/string.go
similarity index 98%
rename from jlib/string.go
rename to v1.5.4/jlib/string.go
index cd49c6f..3ffe032 100644
--- a/jlib/string.go
+++ b/v1.5.4/jlib/string.go
@@ -17,8 +17,8 @@ import (
 	"strings"
 	"unicode/utf8"
 
-	"github.com/blues/jsonata-go/jlib/jxpath"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib/jxpath"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // String converts a JSONata value to a string. Values that are
@@ -231,9 +231,9 @@ func Join(values reflect.Value, separator jtypes.OptionalString) (string, error)
 // regular expression in the source string. Each object in the
 // array has the following fields:
 //
-//     match - the substring matched by the regex
-//     index - the starting offset of this match
-//     groups - any captured groups for this match
+//	match - the substring matched by the regex
+//	index - the starting offset of this match
+//	groups - any captured groups for this match
 //
 // The optional third argument specifies the maximum number
 // of matches to return. By default, Match returns all matches.
diff --git a/jlib/string_test.go b/v1.5.4/jlib/string_test.go
similarity index 99%
rename from jlib/string_test.go
rename to v1.5.4/jlib/string_test.go
index 21a91c6..8b1186c 100644
--- a/jlib/string_test.go
+++ b/v1.5.4/jlib/string_test.go
@@ -13,8 +13,8 @@ import (
 	"testing"
 	"unicode/utf8"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 var typereplaceCallable = reflect.TypeOf((*replaceCallable)(nil)).Elem()
@@ -28,7 +28,7 @@ func TestMain(m *testing.M) {
 		os.Exit(1)
 	}
 
-	if !reflect.PtrTo(typeMatchCallable).Implements(typeCallable) {
+	if !reflect.PointerTo(typeMatchCallable).Implements(typeCallable) {
 		fmt.Fprintln(os.Stderr, "*matchCallable is not a Callable. Aborting...")
 		os.Exit(1)
 	}
diff --git a/jparse/doc.go b/v1.5.4/jparse/doc.go
similarity index 97%
rename from jparse/doc.go
rename to v1.5.4/jparse/doc.go
index 22826d6..c352f34 100644
--- a/jparse/doc.go
+++ b/v1.5.4/jparse/doc.go
@@ -6,7 +6,7 @@
 // syntax trees. Most clients will not need to work with
 // this package directly.
 //
-// Usage
+// # Usage
 //
 // Call the Parse function, passing a JSONata expression as
 // a string. If an error occurs, it will be of type Error.
diff --git a/jparse/error.go b/v1.5.4/jparse/error.go
similarity index 100%
rename from jparse/error.go
rename to v1.5.4/jparse/error.go
diff --git a/jparse/jparse.go b/v1.5.4/jparse/jparse.go
similarity index 100%
rename from jparse/jparse.go
rename to v1.5.4/jparse/jparse.go
diff --git a/jparse/jparse_test.go b/v1.5.4/jparse/jparse_test.go
similarity index 99%
rename from jparse/jparse_test.go
rename to v1.5.4/jparse/jparse_test.go
index f0874e5..91fe085 100644
--- a/jparse/jparse_test.go
+++ b/v1.5.4/jparse/jparse_test.go
@@ -12,7 +12,7 @@ import (
 	"testing"
 	"unicode/utf8"
 
-	"github.com/blues/jsonata-go/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
 )
 
 type testCase struct {
diff --git a/jparse/lexer.go b/v1.5.4/jparse/lexer.go
similarity index 100%
rename from jparse/lexer.go
rename to v1.5.4/jparse/lexer.go
diff --git a/jparse/lexer_test.go b/v1.5.4/jparse/lexer_test.go
similarity index 100%
rename from jparse/lexer_test.go
rename to v1.5.4/jparse/lexer_test.go
diff --git a/jparse/node.go b/v1.5.4/jparse/node.go
similarity index 100%
rename from jparse/node.go
rename to v1.5.4/jparse/node.go
diff --git a/jsonata-server/.gitignore b/v1.5.4/jsonata-server/.gitignore
similarity index 100%
rename from jsonata-server/.gitignore
rename to v1.5.4/jsonata-server/.gitignore
diff --git a/jsonata-server/README.md b/v1.5.4/jsonata-server/README.md
similarity index 100%
rename from jsonata-server/README.md
rename to v1.5.4/jsonata-server/README.md
diff --git a/jsonata-server/bench.go b/v1.5.4/jsonata-server/bench.go
similarity index 98%
rename from jsonata-server/bench.go
rename to v1.5.4/jsonata-server/bench.go
index 925ecfc..0caadab 100644
--- a/jsonata-server/bench.go
+++ b/v1.5.4/jsonata-server/bench.go
@@ -10,7 +10,7 @@ import (
 
 	"encoding/json"
 
-	jsonata "github.com/blues/jsonata-go"
+	jsonata "github.com/blues/jsonata-go/v1.5.4"
 )
 
 var (
diff --git a/jsonata-server/exts.go b/v1.5.4/jsonata-server/exts.go
similarity index 92%
rename from jsonata-server/exts.go
rename to v1.5.4/jsonata-server/exts.go
index 117beb6..97c6eab 100644
--- a/jsonata-server/exts.go
+++ b/v1.5.4/jsonata-server/exts.go
@@ -5,8 +5,8 @@
 package main
 
 import (
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 // Default format for dates: e.g. 2006-01-02 15:04 MST
diff --git a/jsonata-server/main.go b/v1.5.4/jsonata-server/main.go
similarity index 96%
rename from jsonata-server/main.go
rename to v1.5.4/jsonata-server/main.go
index 73ebea0..def3a99 100644
--- a/jsonata-server/main.go
+++ b/v1.5.4/jsonata-server/main.go
@@ -14,8 +14,8 @@ import (
 	_ "net/http/pprof"
 	"strings"
 
-	jsonata "github.com/blues/jsonata-go"
-	"github.com/blues/jsonata-go/jtypes"
+	jsonata "github.com/blues/jsonata-go/v1.5.4"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 func init() {
diff --git a/jsonata-server/site/assets/css/codemirror.min.css b/v1.5.4/jsonata-server/site/assets/css/codemirror.min.css
similarity index 100%
rename from jsonata-server/site/assets/css/codemirror.min.css
rename to v1.5.4/jsonata-server/site/assets/css/codemirror.min.css
diff --git a/jsonata-server/site/assets/css/normalize.min.css b/v1.5.4/jsonata-server/site/assets/css/normalize.min.css
similarity index 100%
rename from jsonata-server/site/assets/css/normalize.min.css
rename to v1.5.4/jsonata-server/site/assets/css/normalize.min.css
diff --git a/jsonata-server/site/assets/css/styles.css b/v1.5.4/jsonata-server/site/assets/css/styles.css
similarity index 100%
rename from jsonata-server/site/assets/css/styles.css
rename to v1.5.4/jsonata-server/site/assets/css/styles.css
diff --git a/jsonata-server/site/assets/js/codemirror.min.js b/v1.5.4/jsonata-server/site/assets/js/codemirror.min.js
similarity index 100%
rename from jsonata-server/site/assets/js/codemirror.min.js
rename to v1.5.4/jsonata-server/site/assets/js/codemirror.min.js
diff --git a/jsonata-server/site/assets/js/javascript.min.js b/v1.5.4/jsonata-server/site/assets/js/javascript.min.js
similarity index 100%
rename from jsonata-server/site/assets/js/javascript.min.js
rename to v1.5.4/jsonata-server/site/assets/js/javascript.min.js
diff --git a/jsonata-server/site/assets/js/jsonata-codemirror.js b/v1.5.4/jsonata-server/site/assets/js/jsonata-codemirror.js
similarity index 100%
rename from jsonata-server/site/assets/js/jsonata-codemirror.js
rename to v1.5.4/jsonata-server/site/assets/js/jsonata-codemirror.js
diff --git a/jsonata-server/site/assets/js/split.min.js b/v1.5.4/jsonata-server/site/assets/js/split.min.js
similarity index 100%
rename from jsonata-server/site/assets/js/split.min.js
rename to v1.5.4/jsonata-server/site/assets/js/split.min.js
diff --git a/jsonata-server/site/favicon.ico b/v1.5.4/jsonata-server/site/favicon.ico
similarity index 100%
rename from jsonata-server/site/favicon.ico
rename to v1.5.4/jsonata-server/site/favicon.ico
diff --git a/jsonata-server/site/index.html b/v1.5.4/jsonata-server/site/index.html
similarity index 100%
rename from jsonata-server/site/index.html
rename to v1.5.4/jsonata-server/site/index.html
diff --git a/jsonata-test/.gitignore b/v1.5.4/jsonata-test/.gitignore
similarity index 100%
rename from jsonata-test/.gitignore
rename to v1.5.4/jsonata-test/.gitignore
diff --git a/jsonata-test/README.md b/v1.5.4/jsonata-test/README.md
similarity index 100%
rename from jsonata-test/README.md
rename to v1.5.4/jsonata-test/README.md
diff --git a/jsonata-test/main.go b/v1.5.4/jsonata-test/main.go
similarity index 96%
rename from jsonata-test/main.go
rename to v1.5.4/jsonata-test/main.go
index 937e07e..2aa9fd1 100644
--- a/jsonata-test/main.go
+++ b/v1.5.4/jsonata-test/main.go
@@ -5,15 +5,14 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
 	"regexp"
 	"strings"
 
-	jsonata "github.com/blues/jsonata-go"
-	types "github.com/blues/jsonata-go/jtypes"
+	jsonata "github.com/blues/jsonata-go/v1.5.4"
+	types "github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 type testCase struct {
@@ -179,12 +178,13 @@ func runTest(tc testCase, dataDir string, path string) (bool, error) {
 // loadTestExprFile loads a jsonata expression from a file and returns the
 // expression
 // For example, one test looks like this
-// {
-//     "expr-file": "case000.jsonata",
-//     "dataset": null,
-//     "bindings": {},
-//     "result": 2
-// }
+//
+//	{
+//	    "expr-file": "case000.jsonata",
+//	    "dataset": null,
+//	    "bindings": {},
+//	    "result": 2
+//	}
 //
 // We want to load the expression from case000.jsonata so we can use it
 // as an expression in the test case
@@ -193,7 +193,7 @@ func loadTestExprFile(testPath string, exprFileName string) (string, error) {
 	splitPath[len(splitPath)-1] = exprFileName
 	exprFilePath := strings.Join(splitPath, "/")
 
-	content, err := ioutil.ReadFile(exprFilePath)
+	content, err := os.ReadFile(exprFilePath)
 	if err != nil {
 		return "", err
 	}
@@ -323,7 +323,7 @@ func equalResults(x, y interface{}) bool {
 }
 
 func readJSONFile(path string, dest interface{}) error {
-	b, err := ioutil.ReadFile(path)
+	b, err := os.ReadFile(path)
 	if err != nil {
 		return fmt.Errorf("ReadFile %s: %s", path, err)
 	}
diff --git a/jsonata-test/main_test.go b/v1.5.4/jsonata-test/main_test.go
similarity index 100%
rename from jsonata-test/main_test.go
rename to v1.5.4/jsonata-test/main_test.go
diff --git a/jsonata.go b/v1.5.4/jsonata.go
similarity index 98%
rename from jsonata.go
rename to v1.5.4/jsonata.go
index 7277b6e..2477a76 100644
--- a/jsonata.go
+++ b/v1.5.4/jsonata.go
@@ -12,9 +12,9 @@ import (
 	"time"
 	"unicode"
 
-	"github.com/blues/jsonata-go/jlib"
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jlib"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 var (
diff --git a/jsonata_test.go b/v1.5.4/jsonata_test.go
similarity index 99%
rename from jsonata_test.go
rename to v1.5.4/jsonata_test.go
index 3267918..6530b9b 100644
--- a/jsonata_test.go
+++ b/v1.5.4/jsonata_test.go
@@ -8,7 +8,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"math"
 	"os"
 	"path/filepath"
@@ -19,8 +18,8 @@ import (
 	"time"
 	"unicode/utf8"
 
-	"github.com/blues/jsonata-go/jparse"
-	"github.com/blues/jsonata-go/jtypes"
+	"github.com/blues/jsonata-go/v1.5.4/jparse"
+	"github.com/blues/jsonata-go/v1.5.4/jtypes"
 )
 
 type testCase struct {
@@ -8094,9 +8093,9 @@ func must(t *testing.T, prefix string, err error) {
 
 func readJSON(filename string) interface{} {
 
-	data, err := ioutil.ReadFile(filepath.Join("testdata", filename))
+	data, err := os.ReadFile(filepath.Join("testdata", filename))
 	if err != nil {
-		panicf("ioutil.ReadFile error: %s", err)
+		panicf("os.ReadFile error: %s", err)
 	}
 
 	var dest interface{}
diff --git a/jtypes/funcs.go b/v1.5.4/jtypes/funcs.go
similarity index 94%
rename from jtypes/funcs.go
rename to v1.5.4/jtypes/funcs.go
index fdbc89b..ebbc168 100644
--- a/jtypes/funcs.go
+++ b/v1.5.4/jtypes/funcs.go
@@ -44,7 +44,7 @@ func IsNumber(v reflect.Value) bool {
 func IsCallable(v reflect.Value) bool {
 	v = Resolve(v)
 	return v.IsValid() &&
-		(v.Type().Implements(TypeCallable) || reflect.PtrTo(v.Type()).Implements(TypeCallable))
+		(v.Type().Implements(TypeCallable) || reflect.PointerTo(v.Type()).Implements(TypeCallable))
 }
 
 // IsArray (golint)
@@ -128,7 +128,7 @@ func AsCallable(v reflect.Value) (Callable, bool) {
 		return v.Interface().(Callable), true
 	}
 
-	if v.IsValid() && reflect.PtrTo(v.Type()).Implements(TypeCallable) && v.CanAddr() && v.Addr().CanInterface() {
+	if v.IsValid() && reflect.PointerTo(v.Type()).Implements(TypeCallable) && v.CanAddr() && v.Addr().CanInterface() {
 		return v.Addr().Interface().(Callable), true
 	}
 
diff --git a/jtypes/types.go b/v1.5.4/jtypes/types.go
similarity index 100%
rename from jtypes/types.go
rename to v1.5.4/jtypes/types.go
diff --git a/testdata/account.json b/v1.5.4/testdata/account.json
similarity index 100%
rename from testdata/account.json
rename to v1.5.4/testdata/account.json
diff --git a/testdata/account2.json b/v1.5.4/testdata/account2.json
similarity index 100%
rename from testdata/account2.json
rename to v1.5.4/testdata/account2.json
diff --git a/testdata/account3.json b/v1.5.4/testdata/account3.json
similarity index 100%
rename from testdata/account3.json
rename to v1.5.4/testdata/account3.json
diff --git a/testdata/account4.json b/v1.5.4/testdata/account4.json
similarity index 100%
rename from testdata/account4.json
rename to v1.5.4/testdata/account4.json
diff --git a/testdata/account5.json b/v1.5.4/testdata/account5.json
similarity index 100%
rename from testdata/account5.json
rename to v1.5.4/testdata/account5.json
diff --git a/testdata/account6.json b/v1.5.4/testdata/account6.json
similarity index 100%
rename from testdata/account6.json
rename to v1.5.4/testdata/account6.json
diff --git a/testdata/account7.json b/v1.5.4/testdata/account7.json
similarity index 100%
rename from testdata/account7.json
rename to v1.5.4/testdata/account7.json
diff --git a/testdata/address.json b/v1.5.4/testdata/address.json
similarity index 100%
rename from testdata/address.json
rename to v1.5.4/testdata/address.json
diff --git a/testdata/foobar.json b/v1.5.4/testdata/foobar.json
similarity index 100%
rename from testdata/foobar.json
rename to v1.5.4/testdata/foobar.json
diff --git a/testdata/foobar2.json b/v1.5.4/testdata/foobar2.json
similarity index 100%
rename from testdata/foobar2.json
rename to v1.5.4/testdata/foobar2.json
diff --git a/testdata/library.json b/v1.5.4/testdata/library.json
similarity index 100%
rename from testdata/library.json
rename to v1.5.4/testdata/library.json
diff --git a/testdata/nest1.json b/v1.5.4/testdata/nest1.json
similarity index 100%
rename from testdata/nest1.json
rename to v1.5.4/testdata/nest1.json
diff --git a/testdata/nest2.json b/v1.5.4/testdata/nest2.json
similarity index 100%
rename from testdata/nest2.json
rename to v1.5.4/testdata/nest2.json
diff --git a/testdata/nest3.json b/v1.5.4/testdata/nest3.json
similarity index 100%
rename from testdata/nest3.json
rename to v1.5.4/testdata/nest3.json