in reply to cut vs split (suggestions)
For your perl test, try using.
perl -lanf, -e 'BEGIN{ $,=','} print @F[0,14];' numbers.csv >out.csv
It may be that at least a part of the difference is the process of joining the values from the slice, before printing them. By setting $, = ',';, you acheive the same affect without forcing perl to build a single concatenation of the values before passing them to print.
I don't have a feel for how big a difference it will make, but it's worth trying.
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