You can tell which rows in which there is one or more missing columns, because split will then return less items.

The

$num_of_columns=@data;
[download]

is not correct, you want

$num_of_columns= scalar( @data );
[download]

Then you can do warn "line $i has only $num_of_columns\n" if $num_of_columns < $wanted_num_of_columns;

But, there is no simple way to find out which column is missing, so you really should try the code wfsp gave you, unpack is your friend here :o)

Try his code, and notice that you can do with a lot less variables than you use. Put the unpack into the loop where you read the file, and then you can test which, if any, of the columns that is empty. It will contain only spaces and therefore will match /^\s+$/