Actually, I had previously tried it using assignment rather than push and the difference was so negligable as to be within the bounds of varience from one run to the next.

C:\test>226666
Benchmark:
running
 substr_it, unpack_it
, each for at least 3 CPU seconds
...

 substr_it:  4 wallclock secs ( 3.17 usr +  0.00 sys =  3.17 CPU) @ 23
+75.99/s (n=7520)

 unpack_it:  4 wallclock secs ( 3.38 usr +  0.00 sys =  3.38 CPU) @ 43
+71.56/s (n=14754)

            Rate substr_it unpack_it
substr_it 2376/s        --      -46%
unpack_it 4372/s       84%        --
Results tally

C:\test>
[download]

I did verify the original as best I could, but as he didn't supply the whole benchmark I had to make a few guesses.

I also attempted to improve both as far as I could as you will see from the update to my first post based upon your suggestion :^)

Older benchmark code for the above results

I'd have to take back my educated guess and go with BrowserUk. I tried this on Solaris and Linux using several different variations and the substr version always comes out over 40% slower. And I did not see the push being twice as slow as the explicit array assignments on either system.

Besides platform, the data being operated on would be the only other factor I can think of that might make the original so much different from what others have tried.