Mabooka % head -1 numbers.csv
462,393,252,996,663,603,344,439,139,259,879,766,545,192,477,986,317,77,611,303,79,742,190,556,538
Mabooka % wc -l numbers.csv
 500000 numbers.csv
Mabooka % 
Mabooka % time perl -lanF, -e 'print join ",", @F[0..4];' numbers.csv > f1
27.820u 0.100s 0:27.92 100.0%   0+0k 0+0io 320pf+0w
Mabooka % time cut -d, -f"1-5" numbers.csv > f2
1.860u 0.100s 0:01.96 100.0%    0+0k 0+0io 100pf+0w
Mabooka % diff f1 f2
Mabooka %