VAR1 = {A => { 
           LEVEL1 => {
              LEVEL1_2 => {
                  LEVEL1_2_3 => {
                     VAL > 'somevalue'
                    }
               }
            }
         }

I am using a if statment with defined in a loop, 
for (my i = 0; i< 3; i++) {
  if (defined $hash->{A}->{LEVEL2}->{LEVEL2_2) { 
     # do something
  } elsif (defined $hash->{A}->{LEVEL1}->{LEVEL1_2) {
     #do something
  }
}