$ time for i in {1..1000}; do perl withListUtil.pl > /dev/null; done

real	0m6.512s
user	0m3.820s
sys	0m2.867s
$ time for i in {1..1000}; do perl withoutListUtil.pl > /dev/null; done

real	0m3.880s
user	0m1.538s
sys	0m2.497s