my %update =
      map {$_ => $inputUpdate{$_} } 
        grep {$inputUpdate{$_} ne $input{$_} }
          keys %input;

$dbh->do(<<"SQL", undef, values %update, $input{ID});
update  TableName
   set @{[ join ', ', map {"$_ = '?'"} keys %update]}
 where ID = ?
SQL
$dbh->commit;