ZiziQue

ZiziQue is a very mysterious esoteric programming language. The only thing known about ZiziQue is that, in it, an implementation of Deadfish might look like this:

[Start] !i^inc"Increment !d^dec"Decrement !s^sqr"Square !o^out"Output . [out] "{number} ^Start [inc] +number ^Start [dec] -number ^Start [sqr] =number,{{number}*{number}} ^Start

Although unless ZiziQue is even weirder than it looks, this seems unlikely to properly implement Deadfish's 256-goes-to-0 behavior.

From this, the commands seem to be:

The example program doesn't show how the input itself works, and variables magically appear similarly to BASIC. It could be that the  command itself inputs if nothing's been input, and removes input if it jumps.