Ampscript Personalization String for Subscriber CreatedDate in Email

I am trying to check the created date for a subscriber upon sending an email to them. I then want to use that value to do something different in the email if the Created Date is today to basically include a welcome section in a triggered send.

I have tried both

Set @CreatedDate = [CreatedDate]Set @CreatedDate = [_CreatedDate]

but they both give the error: The SET variable value expression is invalid.

Is there a better way to do this or what the personalization string is for it?