It's both. As I pointed out, perlbool teaches people who want to learn object oriented programming to use var and use @ISA. If I look at Perldoc, there's use parent. And, at one time I was told this is how you create a constant:
*PI = \3.14159; our $PI;
Now we have use constant.
And, there is a fashion in coding just as much as there is in the dresses in Vogue. We use to tell people to parenthesize everything because it was more readable. Now, we tell people to eliminate unnecessary parentheses because it clutters code and makes it less readable. Variable names use to be camelCase, now we are suppose to use underscores. And, what is the best way to do an infinite loop? Do you use for(;;) or while (1)
Or should that be while ( 1 ) ; because the style is now to leave a space around parentheses and various punctuation marks because it's more readable. However, when I was learning C, I was told to get rid of spaces around parentheses because it made my code harder to read.
I'm just happy I never learned about use English; until I was told that it shouldn't be used because it makes your programs run slower and it doesn't really make your programs more readable anyway.