perl -MTime::HiRes=time 
-E"$m=1e5;$x='x'x$m; $t=time; $n=()=$x=~m[x]g; say +(time()-$t)/$m"
1.44867897033691e-006

perl -MTime::HiRes=time 
-E"$m=1e6;$x='x'x$m; $t=time; $n=()=$x=~m[x]g; say +(time()-$t)/$m"
1.46089999675751e-005