A trip down memory lane ...

I reached across my desk and grabbed my original (pink) version of the Camel book. After blowing off a decade or two's worth of dust, I had a look around.

In "Chapter 3 The Gory Details" (pp. 65-121); under the "Packages" section (pp.119-121); I found on page 120:

    local(*foo) = *bar;
    local($_main{'foo'}) = $_main{'bar'};
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... the *foo is more efficient because it does the symbol table lookup once at compile time ...

Also of nostalgic interest was the use of $main'var instead of $main::var. I haven't used the former version in over 20 years; however, it's still valid:

$ cat pm_11137628_pkg_sep.pl
use strict;
use warnings;

our $x = 42;
print $], "\n";
print $main'x, "\n";
print $main::x, "\n";
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$ perl pm_11137628_pkg_sep.pl
5.034000
42
42
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"foo(*arr1,*arr2)"

Under the "Subroutines" section (pp. 99-102); on page 99; I note a small syntax change is required:

"A subroutine is called using the do operator or the & operator. The & operator is the preferred form."

However, other than that small syntax change, the gist of what you wrote is correct. There's an example on page 102:

    sub arrayadd {
        local(*a, *b) = @_;
        ...
    }
    
    @foo = (1,2,3);
    @bar = (10,20,30);
    @totals = &arrayadd(*foo, *bar);
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The "trip down memory lane" concludes. I hope that was an interesting read. I do acknowledge that it was way off-topic with respect to the OP subject.

Use of the apostrophe as the package separator might soon be a thing of the past also.

https://www.nntp.perl.org/group/perl.perl5.porters/2021/08/msg261286.html

To be honest, I was surprised to find that it was still valid in v5.34 — thanks for the info.

I had written, "I haven't used [it] in over 20 years"; upon reflection, I believe my last usage was probably in 1996 or 1997; so that's closer to a quarter of a century.

The message, to which you linked, had "... $user's problem ...", followed by "This bites experts and new users alike ...". I suspect I could have been one of those bitten, if reviewing another's code without "use warnings;". In v5.28, a new warning was added: see "perl5280delta: New Warnings" and "perldiag: Old package separator used in string". My normal code would be something along these lines:

ken@titan ~/tmp
$ cat pm_11137628_pkg_sep_in_string.pl
use strict;
use warnings;

my $user = 'ken';

print "... $user's problem ...\n";
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which, when run, gives me ample feedback:

ken@titan ~/tmp
$ perl -v

This is perl 5, version 34, subversion 0 (v5.34.0) built for cygwin-th
+read-multi
...

ken@titan ~/tmp
$ perl pm_11137628_pkg_sep_in_string.pl
Old package separator used in string at pm_11137628_pkg_sep_in_string.
+pl line 6.
        (Did you mean "$user\'s" instead?)
Name "user::s" used only once: possible typo at pm_11137628_pkg_sep_in
+_string.pl line 6.
Use of uninitialized value $user::s in concatenation (.) or string at 
+pm_11137628_pkg_sep_in_string.pl line 6.
...  problem ...
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I don't have anything earlier than v5.30 on that system:

$ perlbrew list
 * perl-5.34.0
   perl-5.33.5
   perl-5.32.0
   perl-5.30.0
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However, on another OS:

C:\Users\ken\tmp>perl -v

This is perl 5, version 26, subversion 3 (v5.26.3) built for MSWin32-x
+64-multi-thread
...

C:\Users\ken\tmp>perl pm_11137628_pkg_sep_in_string.pl
Name "user::s" used only once: possible typo at pm_11137628_pkg_sep_in
+_string.pl line 6.
Use of uninitialized value $user::s in concatenation (.) or string at 
+pm_11137628_pkg_sep_in_string.pl line 6.
...  problem ...
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Not quite as "ample" feedback. I expect I could work it out from here; others might be saying frustratedly: 'But there is no "user::s" in my code'.

I read through about the first dozen NNTP messages. Most discussion seemed to be about whether removal should be partial or complete, and backward-compatibility. When I got to https://www.nntp.perl.org/group/perl.perl5.porters/2021/08/msg261321.html and read "... disks of infinite size coming free with a packet of corn flakes ...", I had a chuckle and left it there. I wouldn't personally have any problem if the old style package separator was removed permanently and completely.

— Ken

Didn::t know that. Thanks for letting us know.

Though it puts a crimp on Perl joke modules, there don::t appear to be enough of those to warrant keeping it -- the only one I remembered without googling was Chris Nandor's classic Do'h, released before the CPAN Acme namespace was born.

This is all I could find:

• Do'h by Chris Nandor
• D'oh::Year by Mick Schwern
• Acme::Don't by Damian Conway
• Test::More - this core module uses a typeglob alias (sub isnt { ... } *isn't = \&isnt) to allow you to write isn't in your tests instead of isnt ... hardly a critical feature. :)