How to do Compound Conditionals?

I have a variable which can take on any of 50 values. For two of those values I want to do a certain step. For all the rest I want to do a different step. So, what I want is:

If ($Var = A) OR ($Var = B)
Command set 1.
Else
Command set 2.

Command set 2 cannot be executed UNLESS $Var <> A AND $Var <> B,
so I can't just run Command set 2, and then put Command set 1 into 2 clones with the simple conditions $Var = A, $Var = B.

If I can't do the compound conditionals, I'm thinking I have to put this into 50 steps:

If $Var = A
Command Set 1.
If $Var = B
Command Set 1.
If $Var = C
Command Set 2.
.
.
.

What's the best way to do this?

Thanks,
John Bobinyec