$ perl5.24.1 -v

This is perl 5, version 24, subversion 1 (v5.24.1) built for x86_64-linux-thread-multi
[...]

$ time perl5.24.1 every-second-item-reversed-haukex.py in.txt > haukex-out-5.24.1.txt

real	0m1.759s
user	0m1.740s
sys	0m0.016s