If you memory and or execution times are so important for your project that you have to consider these decisions for trivial code like this, your biggest mistake is to use Perl.

Perl shines in many things of which making it the programmer easy isn't the least of things. But they come with a price. Perl does a lot of bookkeeping behind the scenes. Which costs time and memory.

Seriously, if memory usuage and/or CPU usage for trivial code matters to you, use C, not Perl. That's were C shines.