Comment by seertaak

First, let's distinguish between two types of syntactic constructs: null and left denominations. (Terminology borrowed from Pratt parsers.) Null denominations can exist on their own, left denominations can't -- they are inherently chained (eg arithmetic expressions, statements in a block, or elements of a tuple), and allow a succinct, infix notation for variable-length constructs (no lispy parentheses hell).

Second, null denominations usually introduce names -- whether for variables, types, functions, lifetimes, macros, etc. One exception to this are free-standing value expressions (a bit weird; less so when they're the last expression in a block indicating the value returned by it). Another other exception would be directive type constructs - eg directives to import names from another module, directives to give hints to the compiler, etc. The last two exceptions are the most common ones: variable assignment and function invocation.

The golden rule of good language design, as I see it, is this: null denominations must begin with a fixed and unique token. The only permissible exceptions should be for assignment and function invocation; exceptions which exist because those use-cases appear so often in a typical program that requiring a prefix would be insufferable.

Julia breaks this rule for global variables. (Fair enough, Python also commits this error, but it's a mistake and a source of bugs!) But wait, Julia also has "const" and "local" binding constructs, where it follows the golden rule -- but now your syntax isn't consistent. So now you need to keep in your head these nuances -- and know the difference between a soft and hard scope -- when you want to write a function which modifies a function using macrology.

(As a point of taste on the choice of prefix token: introduction of variables through "local" is just as weird as C++'s "auto" -- and at least Bjarne Stroustroup had an excuse for that choice. Anyone who introduces a global variable in a local scope should be punished imho, so there's no need to say "this is a local variable", it's obvious from the fact that the name is introduced inside a function. Instead, my personal preference is to introduce constants through "let", and variables through "var". The former is well-known to anyone numerate, and the latter is ubiquitous in software engineering. Both read well; they're as close as possible as you can get to constructs in English.)

Julia breaks the golden rule again with its succinct, Mathematica-style notation for function definition. I get that it wants to appeal to Mathematica users, but Python already proved you don't need to do that. This is a programming language; brainy types, like mathematicians and physicists, aren't going to be flummoxed by an unfamiliar notation for function definition, or irritated by having to type a few extra characters.

I mention macrology; it's not just that. Let's say you want write a syntax highlighter -- you need to take into account all that weirdness. If null denominations have a fixed & unique prefix, parsing is easy-peasy. Want to add a capability to "inline" HTML code within Julia, react-style? You're going to run into similar issues. And so on...