It is not clear why you are diddling the data, what you call "format the columns", so why are you? You should do that after parsing into cvs, not before

Somehow I have a feeling that this code is not efficient but it works.

Thats just gas, don't worry about it

Is it worth to improve it or just use it as it is?

The code is literally 20 lines, there is nothing to improve

The only possible thing is use "modern perl" practices, meaning use 3 argument open, and lexical filehandle, and maybe use autodie because the error message is better

$ perl -Mautodie -le " open my $fh => '<', '23232' "
Can't open '23232' for reading: 'No such file or directory' at -e line
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