Candidate groups expression language

Which expression language can be used in within the Candidate groups field of a user task? I would like to use a loop within the field that loops over values within an array process variable. This documentation User tasks | Camunda 8 Docs links to FEEL as expression language, but a simple FEEL example I made lead to an error:
The expression was ${for test in [“2c92808a-9053c45b-0190-53c49adf-0005”] return test} and I got the error “ENGINE-01009 Error while parsing process. Error parsing ‘${for test in [“2c92808a-9053c45b-0190-53c49adf-0005”] return test}’: syntax error at position 6, encountered ‘test’, expected ‘}’.”