Is this still a sound advice to give these days? The doc that you link to says:
in reply to Re: How does one get all possible matches from regex?
in thread How does one get all possible matches from regex?
As of the 5.005 release, the $& variable is no longer "expensive" the way the other two are.
Why Is $& Bad? gives a better technical explanation why one might want to avoid $&. Even so, the issue with $& is perhaps more of a concern for core module writers. Can you point to some recent benchmarks?
On a related note, does study() actually do anything in more recent perls?