Does just running the code you show have the slowdown?  If not, the problem is in the code that actually processes each @temp2array chunk, perhaps some variable(s) still having data left over from previous chunks.

Slowdown in large perl array
I am using the ATMEL ARM SAM4S MCU for a project. It supports a single-supply mode where an internal voltage regulator provides the 1.08-1.32V necessary for VDDCORE and we need only provide 1.62-3.6V to VDDIO. 

I'm just interested to know if there is any situation where one might NOT take advantage of this feature and supply the core externally as well?
