The oddest lesson of Perl is that, even though there’s a million ways to do it, not all of them are used. It turns out that coders generally realize that the constructed examples you show above are all problematic for reasons unrelated to the change!

“What is b-c, is that a variable or a math?”

“Is it (a=b-c)+d or a=(b-c+d)”

So you simply wouldn’t encounter code written like this, because it’s just as confusing as it is problematic for the hyphen change.