VM instruction implementation without huge switch()?

How would one go about making a virtual machine without using a huge and clumsy switch( opcode ) statement?

The architecture I'm implementing (DCPU-16) has about 35-40 different instructions.

>>3
switch is not constant. Its upper bound is N. If the opcode being executed is the last opcode in your switch, you need to make N, or in this case 40, comparisons, whereas lg(40) = 5.

A switch would be better if you know that certain opcodes will be executed from frequently than others, in which case you can order your switch by the frequency of the opcode.