This works: sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"

##</code><code>##

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time wc lesms10_big.txt 
 14152200 113528600 652751200 lesms10_big.txt

real 0m3.412s
user 0m3.307s
sys  0m0.097s

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time ./wc.pl lesms10_big.txt
 14152200 113528600 652751200 lesms10_big.txt

real 0m0.613s  (5.57x)
user 0m4.168s
sys  0m0.432s

##</code><code>##

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time ./wc.pl --max-workers=8 lesms10_big.txt
 14152200 113528600 652751200 lesms10_big.txt

real 0m0.613s  (5.57x)
user 0m4.168s
sys  0m0.432s

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time ./wc.pl --max-workers=12 lesms10_big.txt
 14152200 113528600 652751200 lesms10_big.txt

real 0m0.454s  (7.52x)
user 0m4.464s
sys  0m0.536s

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time ./wc.pl --max-workers=16 lesms10_big.txt
 14152200 113528600 652751200 lesms10_big.txt

real 0m0.360s  (9.48x)
user 0m4.344s
sys  0m0.625s

##</code><code>##

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time wc lesms10_big.txt 
 14152200 113528600 652751200 lesms10_big.txt

real 0m3.412s
user 0m3.307s
sys  0m0.097s

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time ./wc.pl --max-workers=1 lesms10_big.txt
 14152200 113528600 652751200 lesms10_big.txt

real 0m3.553s
user 0m3.363s
sys  0m0.329s

$ sudo bash -c "echo 1 >/proc/sys/vm/drop_caches"
$ time ./wc.pl --max-workers=2 lesms10_big.txt
 14152200 113528600 652751200 lesms10_big.txt

real 0m1.804s
user 0m3.339s
sys  0m0.357s