Configure Event Rule Payload as parametrised bucket

I am defining BucketName which will take user input as a list of bucket separated by ",". I want to use these buckets in the request parameters section of EventRule

Description: Template to create AWS Event Bridge
Parameters:
  BucketName:
    Type: String
    Default: "Enter Bucket Name1,BucketName2"

Resources: 
  
  EventRule: 
      Type: AWS::Events::Rule
      Properties: 
        Description: "EventRule"
        State: "ENABLED"
        EventPattern: 
          source: 
            - aws.s3
          detail: 
            eventSource: 
              - "s3.amazonaws.com"
            eventName: 
              - PutObject
              - DeleteObject
            requestParameters:
             bucketName:
              - Fun::Split: [",", !Ref BucketName]

But it is throwing following error message

Event pattern is not valid. Reason: Unrecognized match type Fun::Split at [Source: (String)"{"source":["aws.s3"],"detail":{"eventSource":["s3.amazonaws.com"],"requestParameters":{"bucketName":[{"Fun::Split":[",",""abc,def""]}]},"eventName":["PutObject","DeleteObject"]}}"; line: 1, column: 117] (Service: AmazonCloudWatchEvents; Status Code: 400; Error Code: InvalidEventPatternException; Request ID: d80f531a-660d-4f4c-b9ab-70cb4507bf05; Proxy: null)

It should be Fn::Splitm not Fun::Split.