What is the purpose of local *_ = \my $a in File::Find?

[YenForYang]

I was looking through the source code of Find.pm of File::Find. The comments mention why local()-izing is needed, which I kinda-sorta understand since the the callback functions passed in may call find or finddepth again, so local essentially makes a copy of the global variables (am I right or wrong here?). However, I don't understand why local *_ isn't sufficient. Why is set to \my $a? Why \my $a in particular and not some other variable--I mean, could any variable substitute \my $a? Thanks.

[ikegami]

local $_ could be used to localize $_, but that doesn't remove any magic associated with it on some versions of Perl.

$ perl -wE'for ($|) { local $_; $_ = "abc"; say; }'
Argument "abc" isn't numeric in scalar assignment at -e line 1.
0

local *_ would do the trick by forcing an entirely new $_ to be created, but that also gets rid of @_, %_, etc.

$ perl -E'$_="x"; @_=(4,5); say $_,@_; local *_; say $_,@_;'
x45

Assigning to a glob is weird, though. It only assigns to the relevant slot. So that means assigning a reference to a scalar to *_ only replaces $_

$ perl -E'$_="x"; @_=(4,5); say $_,@_; local *_ = \my $a; say $_,@_;'
x45
45

Any fresh scalar would have worked.

Note that this aliases $_ to the scalar, but File::Find does not take advantage of that feature.

[YenForYang]

Awesome, thanks for the explanation.

What do you mean though by

Note that this aliases $_ to the scalar, but File::Find does not take advantage of that feature.

Specifically the part about not taking advantage of the feature. What features could be taken advantage of? Thanks

EDIT:

Oh wait are you saying that $a could be used like $_ (they become equivalent?). Or is there something else?

[ikegami]

$ perl -E'local *_ = \my $s;  $_ = 123;  say $s;  $s = 456;  say $_;'
123
456