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perl -pi -e 'split/\t/;map{$_.=q/ /x4;substr$_,0,4*int length($_)/4}@_ +' filename.txt
perl -pi -e 'while(/\t/g){$d=(4-pos%4)%4+1;$x=q/ /x$d;s/\t/$x/}' filen +ame.txt