title: Is there a allowed pattern regex to validate List<AWS::EC2::AvailabilityZone::Name>
body: <p>I wanted to have a regex to ensure user provides 2 elements to parameter which is List</p>
  
  <p><code>AvailabilityZones:
      Description: List of Availability Zones to use for the subnets in the VPC. Only
        two Availability Zones are used for this deployment, and the logical order of
        your selections is preserved.
      Type: List&lt;AWS::EC2::AvailabilityZone::Name&gt;
      AllowedPattern: "(([a-zA-Z]+)-([a-zA-Z]+)-([0-9a-z]+))"
      ConstraintDescription: Two Availability Zones must be added.
  </code></p>
  
  <p>The above pattern does not validate 2 entries. Can someone help share how to effectively handle this scenario.</p>