I am attempting to use `sed` to replace a regular expression capture group. I've read that this requires enabling extended regular expressions with the `-E` flag. However, the following command is still not updating the text as expected.

```sh
echo "master-abcdef" | sed -i '' -E "s/IMAGE_TAG:\s*(\S+)$/\1/g" values.yaml

```

Where `values.yaml` has contents of:

```
global:
  env: default

default:
  IMAGE_TAG: dev-0be3323.zgm9a
  ... (more text below)

```

I am expecting `values.yaml` to be replaced to:

```
global:
  env: default

default:
  IMAGE_TAG: master-abcdef
  ... (more text below)

```