I think we would all agree that documenting every line of your code (with parens, formatting, spacing, pod, comments etc etc) is too much:

$a = 3;  # Set the global variable called a (which is a scalar variable, meaning that it can hold either a number or a string - in this case we are using a string) blah blah...

Is not a "moderate" amount of documentation.

Writing your entire program on one-line is also not a "moderate" amount of documentation.

So somewhere in between the two extremes lay a "moderate" amount of attention to readability and documentation.

My statement is that at that point of moderation - in most professional environments - it *should* be expected that the reader knows the precedence table - and therefore documentary parenthesis are not necessary.