Simple answer: You can't. You can't define an operator (like a op b) at all, you can only define functions (like f(a,b)). Functions are sometimes called list operators (mostly because you can call them without parens), but I think doing that confuses the issue. Moreover, you can only define functions that fit in a limited namespace: /^A-Za-z_A-Za-z_0-9+$/ (you might be able to get around this with symref magic... but I wouldn't recommend trying).

Complicated answer: you can use source filters to do arbitrary transforms on your code before perl compiles it. See Filter::Simple. While this can certianly do what you want (assuming what you want to do is possible), it's almost certianly really difficult. (Best-case scenario is that you can crib off of Switch or somthing similar.)

We are using here a powerful strategy of synthesis: wishful thinking. -- The Wizard Book