in reply to Variable declaration optimization?

Before we tell you which one is a few nano-seconds faster, you have to tell us what you're going to do with the time you save.

There's also initializing them with a list ... generally better with constants.

my ( $var1, $var2 ) = ( $FIRST_INDEX, $SECONDS_IN_A_YEAR );

As Occam said: Entia non sunt multiplicanda praeter necessitatem.