The AWS CLI supports the following environment variables.

• AWS_ACCESS_KEY_ID – AWS access key.
• AWS_SECRET_ACCESS_KEY – AWS secret key. Access and secret key variables override credentials stored in credential and config files.
• AWS_SESSION_TOKEN – Specify a session token if you are using temporary security credentials.
• AWS_DEFAULT_REGION – AWS region. This variable overrides the default region of the in-use profile, if set.

See the official documentation

The official boto client support these variables

erlcloud fails because it uses outdated variables AWS_SECURITY_TOKEN and AWS_REGION