I have a Kafka client container running on AWS ECS, which should receive a regular expression for which topics to subscribe to from the containers environment variables. In my terraform I define the environment variable like so:

```
..
      {
        "name": "KAFKA_TOPIC_REGEX",
        "value": "${local.kafka_topic_regex[local.environment]}"
      }
..

```

With a corresponding value in the locals.tf file like so:

```
..
  kafka_topic_regex = {
    development = "^(ab\..*\..*)$|^(foo\.bar)$"
  }
..

```

However I'm having difficulty getting this to work as expected. When I terraform plan, the following error is shown:

```
The symbol "." is not a valid escape sequence selector.

```

Unfortunately I need the backward slash there for the regex to use the literal dot as a character in the topic name. I can't escape the backward slash as I actually require it be there for the regex.

I have equally tried the regex like so:

```
^(ab[.].*[.].*)$|^(foo[.]bar)$

```

Again, Terraform does some strange interpretation of this and in the plan the value appears as:

```
^ab.(.*)

```

This will mean that the literal dot I require isn't in the regex as it is required to be escaped in the regex.

It appears Terraform is interpreting my string and causing a failed plan / apply, when it shouldn't be interpreting it.

Any help would be appreciated, thank you