$ rm -f out; time perl demo.pl | LC_ALL=C sort -k2rn > out
real   0m34.779s
user   1m39.925s
sys    0m00.555s

$ rm -f out; time perl demo.pl | LC_ALL=C parsort -k2rn > out
real   0m04.484s
user   1m17.538s
sys    0m00.575s

$ rm -f out; time perl demo.pl | LC_ALL=C mcesort -k2rn > out
real   0m04.287s
user   1m54.859s
sys    0m01.748s