diff --git a/internal/iofilter/filter.go b/internal/iofilter/filter.go
new file mode 100644
index 0000000..4316bb5
--- /dev/null
+++ b/internal/iofilter/filter.go
@@ -0,0 +1,32 @@
+// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
+
+package iofilter
+
+import (
+	"io"
+	"log/slog"
+)
+
+type ReadFilter func([]byte, int, error) (int, error)
+
+type Reader struct {
+	input io.Reader
+	filter ReadFilter
+}
+
+func NewReader(reader io.Reader, filter ReadFilter) *Reader {
+	return &Reader{
+		input: reader,
+		filter: filter,
+	}
+}
+
+func (r *Reader) Read(p []byte) (n int, err error) {
+	n, err = r.input.Read(p)
+	if r.filter != nil {
+		return r.filter(p, n, err)
+	} else {
+		slog.Warn("iofilter.Reader.Read() - nil filter") 
+	}
+	return n, err
+}
diff --git a/internal/iofilter/filter_test.go b/internal/iofilter/filter_test.go
new file mode 100644
index 0000000..f1cf307
--- /dev/null
+++ b/internal/iofilter/filter_test.go
@@ -0,0 +1,22 @@
+// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
+
+package iofilter
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+	"strings"
+)
+
+func TestNewReader(t *testing.T) {
+	buffer := make([]byte, 20)
+	reader := NewReader(strings.NewReader("testdata"), func(p []byte, in int, e error) (int, error) {
+		copy(p, []byte("foo"))
+		return 3, nil
+	})
+	assert.NotNil(t, reader)
+	sz, e := reader.Read(buffer)
+	assert.Nil(t, e)
+	assert.Equal(t, 3, sz)
+	assert.Equal(t, "foo", string(buffer[:3]))
+}
diff --git a/internal/resource/schemas/package.jsonschema b/internal/resource/schemas/package.jsonschema
index 72e0628..32ae8b6 100644
--- a/internal/resource/schemas/package.jsonschema
+++ b/internal/resource/schemas/package.jsonschema
@@ -12,7 +12,7 @@
     "required": {
       "description": "version requirement",
       "type": "string",
-      "pattern": "^([><~=][=]?[a-zA-Z0-9+.-_]+|)$"
+      "pattern": "^(([><~]*=){0,1}[-_a-zA-Z0-9+.]+|)$"
     },
     "version": {
       "type": "string"