I will not bother to find out where the break-even point on my system lies. As chromatic says, the milliseconds saved are unimportant. If they would be important, I would neither use a Perl if-else chain, nor a Perl dispatch table. Instead, I'd write a piece of C code (which could be an if/else chain, a switch or a dispatch table).

Luckely for me, most of the time, the milliseconds are not important, and I can use both Perl, and whatever technique I find more readable/maintainable.