# $Var2 is a reference to the first-level hash
  $rh2 = $Var2->{'ClaimBaseInfoDT'};
  # $rh2 is now a reference to one of the second-level hashes
  #   contained within the first
  $claimday = $rh2->{'ClaimDay'};
  # which you can use to access the inner-most values

  # You can do it all in one step, too
  $claimday = $Var2->{'ClaimBaseInfoDT'}->{'ClaimDay'};