This example dies under strict with Can't use string as a HASH ref and would "survive" with faulty magic after strict was removed.

For this not to be noticed under strict the symbolic ref has only to happen occasionally.

So yes it has an effect on runtime, but this is "only" exchanging one (fatal) bug with a weird bug in edge cases.

So what could happen is that someone thought removing strict fixed the bug in a long running script, which eventually produced broken data.

Well ... I think we agree that removing strict is not a good idea anyway.

One might only be able to make a case for short scripts and one-liners. But the longer you wait to activate strict the more expensive it gets.