None of those steps are skipped. The check needs to be performed if nothing else.

I'm just saying that (re)assigning a string to a variable already containing just a string (i.e. only the PV slot allocated, no magic attached) is comparably cheap compared to all the "whatnot" the perl intepreter does. Is this incorrect?

hmmm. The long list of checks I mentioned and similar ones are constantly being made. It's is quite a drain.

Is it cheap compared to the rest that Perl does? If you mean the guts of operations like doing a regex match or making a system call? sure. But compared to overheads in Perl? not really. (The things you identified basically happen at compile-time, except for what amounts to a C struct lookup. They're definitely not drains!)

Then the OP makes a valid point.

They do. You could get great speed boosts if you could leave out a lot of checks.