Petunia is an esoteric programming language. it uses prefix notation for everything, meaning you don't need paranthesis for precedence. Even control flow follows prefix notation, for example if statements expect three operands; something that evaluates to true or false, and then two expresions. the if statement only evaluates the second or third value depending on the first, and passes on that value.
Petunia source files typically use the PNL extension, although other file extensions can work as well. To run a Petunia program, use the command python interpreter_petunia.py [source file]. The interpreter requires Python 3.10 or above to work. The current interpreter is fairly limited, and doesn't yet support strings, or generics.
For more information about petunia, refer to this language design doc: https://docs.google.com/document/d/15LhwX6dlZS_UaPzdla8M7EqI0XKBfqQNEcw5ZqY2wFE/edit?usp=sharing