Getchl

Getchl is an esoteric shell designed for WalrusOS that uses  as its primary form of input. Every time a keystroke occurs, Getchl executes a command. This makes it an esoteric shell in that it uses irregular forms of user interaction, coupled with the esoteric programming language used (which is really just a standard stack-based golfing language).

Data Model
In one of my favorite data model families, the model behind Getchl is a both-sides-infinite tape of byte stacks with a scalar accumulator.

Terminology
All values are modulo 256 (or not, for a unicode implementation).

Command List
All commands are subject to change. Feel free to suggest such changes yourself.

Prime Mode Commands
Prime mode is an interpreter mode where commands are executed with alternative meanings. Unless otherwise specified, the interpreter returns to default mode after execution.

Failure Codes
Some commands can return failure codes when executed under certain conditions. Failure codes do not terminate the script. All failure codes are negative.

Useful Constructs and Mnemonics