time perl -le '$x=1e9;$y=0;$y+=$_ for 1..$x;print$y'
500000000500000000

real	0m26.796s
user	0m26.617s
sys	 0m0.088s

time mce (your script)
500000000500000000

real	0m7.323s
user	0m55.095s
sys	 0m0.127s