$ time perl -lanF, -e 'print join ",", @F[0..14];' numbers.csv > /dev/null

real    0m9.880s
user    0m9.716s
sys     0m0.034s

##</code><code>##

$ time perl -lanF, -e 'BEGIN{ $,=","} print @F[0..14];' numbers.csv > /dev/null

real    0m8.974s
user    0m8.772s
sys     0m0.042s

##</code><code>##

$ time perl -ln -e 'print $1 if /((?:[^,]+,){14}[^,]+)/' numbers.csv > /dev/null

real    0m3.412s
user    0m3.370s
sys     0m0.031s