intrinsic functions

stepfunction.json

{
  "Comment": "A Catch example of the Amazon States Language using an AWS Lambda Function",
  "StartAt": "nextstep",
  "States": {
    "nextstep": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-central-1:1234567890:function:catcherror",
      "Parameters": {
                    "executionId.$": "States.Format('somestring {}', $$.Execution.Id)"
      },
      "End": true
    }
  }
}

corresponding output from function

{'executionId': 'somestring arn:aws:states:eu-central-1: 1234567890:execution:Catchfailure:2e7a5795-1d12-7a50-936c-47d8fbaf301d'}

In this what you are looking for like a random string , that too is not returned by $$.Execution.Id. So would be good to use a lambda to generate the string and use that for further States.Format

{
  "Comment": "A Catch example of the Amazon States Language using an AWS Lambda Function",
  "StartAt": "nextstep",
  "States": {
    "nextstep": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-central-1: 1234567890:function:catcherror",
      "ResultPath": "$.randomstring",
      "Parameters": {
        "executionId.$": "States.Format('somestring {}', $$.Execution.Id)"
      },
      "End": true
    }
  }
}

outputs execution id by parsing arn:aws:states:eu-central-1: 1234567890:execution:Catchfailure:2e7a5795-1d12-7a50-936c-47d8fbaf301d

{
  "Comment": "A Catch example of the Amazon States Language using an AWS Lambda Function",
  "StartAt": "nextstep",
  "States": {
    "nextstep": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-central-1: 1234567890:function:catcherror",
      "ResultPath": "$.randomstring",
      "Parameters": {
        "executionId.$": "States.Format('somestring {}', $$.Execution.Id)"
      },
      "Next": "Pass"
    },
    "Pass": {
      "Type": "Pass",
      "OutputPath": "$.randomstring",
      "End": true
    }
  }
}

output :

{
  "Comment": "A Catch example of the Amazon States Language using an AWS Lambda Function",
  "StartAt": "nextstep",
  "States": {
    "nextstep": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-central-1:1234567890:function:catcherror",
      "ResultPath": "$.randomstring",
      "Parameters": {
        "executionName.$": "$$.Execution.Name"
      },
      "Next": "PassRandomeString"
    },
    "PassRandomeString": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-central-1: 1234567890:function:mytestfunction",
      "Parameters": {
        "randomstring.$": "$.randomstring"
      },
      "End": true
    }
  }
}