Well, first of all you made mistake, the line 6 is where the assignment is done.

:)

Second, if you separate the assignment from localizing, then no warning is produced.

um, put that in the code?

use warnings;
sub RO { warn "RO" }
sub SHAM { warn "SHAM" }
RO();
{ local *RO = sub { warn "BO" }; RO(); }
SHAM();
{ local *SHAM; *SHAM = sub { warn "BO" }; SHAM(); }
RO(); SHAM();
__END__
RO at - line 2.
Subroutine main::RO redefined at - line 5.
BO at - line 5.
SHAM at - line 3.
BO at - line 7.
RO at - line 2.
SHAM at - line 3.
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So, that kinda makes sense to me, when its redefined, you get warning

When its undefined, then its defined , you get no warning

So , to see if its a bug , I look at what warnings says which is

Subroutine %s redefined

(W redefine) You redefined a subroutine. To suppress this warning, say

    {
    no warnings 'redefine';
    eval "sub name { ... }";
    }
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So my new code snippet is

$ perl -le " use warnings; sub foo { warn 1 } foo(); local *foo; sub f
+oo { warn 2 } foo(); "
Subroutine foo redefined at -e line 1.
2 at -e line 1.
Undefined subroutine &main::foo called at -e line 1.
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Hmm, at compile time its redefined, but at run time its undefined

Oh right, eval

$ perl -le " use warnings; sub foo { warn 1 } foo(); local *foo; eval 
+q{sub foo { warn 2 }}; foo(); "
1 at -e line 1.
2 at (eval 5) line 1.
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no redefined warning is given

And third take round trip

$ perl -le " use warnings; sub foo { warn 1 } foo(); { local *foo; eva
+l q{sub foo { warn 2 }}; foo(); } foo(); "
1 at -e line 1.
2 at (eval 5) line 1.
1 at -e line 1.
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no redefined warning is given

So , yup, the situation makes sense from a technical point, at the time the new sub is defined, the old sub doesn't exist in the current scope -- current stash -- it doesn't exist

Could perl/warnings be made to detect this case? Sure

Would it be worth it? I doubt it -- its essentially double checking

So, I don't see it as a bug or undesireable; I don't see a compelling reason to change it

Cheers