entrypoint.sh – line 9: syntax error: unexpected "("

I am trying to run the following script from docker (based on alpine image)

#!/bin/sh

echo "test"

export USERNAME="AQICAHj456mvH8iSJofL46Xtr7KP6Ng3Vn5k6BpZbkAAAAZTBjBgkqhkiG9w0BBwagVjBUAgEAME8GCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMwCm8C+wSLRm/+sSuAgEQgCJHCFbrIwCQuH0x2iGp13j9SuxMtfrcE6c4SmrHRVkkX24f"
export AWS_REGION="us-east-1"
echo "$AWS_REGION"

decrypt=$(aws kms decrypt --ciphertext-blob fileb://<(echo "$USERNAME" | base64 -d))
export $key="$(echo $decrypt | jq .Plaintext -r | base64 -d)"

exec "[email protected]"

I am getting the below output

test
us-east-1
/bin/entrypoint.sh: line 9: syntax error: unexpected "("

I am not sure how to resolve this syntax error. Any help is appreciated.

Source: StackOverflow