Yea...it uses "de" to define a function instead of "defun". People always hate on it for no macros, but macros don't make since when you only have an interpreter. I don't fully understand how, but I've heard people in the past explain how they're irrelevant in Picolisp and how you can still extend the syntax with standard functions somehow. Maybe a picolisper could give some examples?
Shout out that there are two free online books on Picolisp.
You dont need macros as you have fexpr's which don't evaluate it's arguments. It fits much better into the language, and they are first class. See https://picolisp.com/wiki/?prosandcons
More importantly it doesn't need lambda, just lists, and quote quotes all arguments not just the first one. An extremely simple and small lisp-1 interpreter, comparable to the old AutoLISP.
Shout out that there are two free online books on Picolisp.