A Perl array is a list, and a Perl hash is (unless "tied") a hash-table. All very-cleverly implemented for you by some very-clever people, long ago.

Dictum Ne Agas:   Do Not Do A Thing Already Done.

Focus on your problem:   the “what,” not the “how.”

Do not be overly concerned about the poor ol' CPU, because... “at hundreds of millions of operations per second, no one can hear you scream.” Just make sure that your algorithm is efficiently and sensibly designed, and leverage existing platforms (like Perl itself, and CPAN) to the greatest possible extent.

Don't "diddle" code to make it faster:   Choose a better algorithm.