AFAIK you are reproducing the import mechanism 100% (a glob from one STASH gets a reference to a fully qualified package var assigned)

Apparently Perl is setting a flag then, indicating that the target $var doesn't need to be oured anymore under strict.

The only "special" thing is that you found a back-door to import from the same package.

The first example that doesn't work seems to highlight an implementation detail, that the surrounding package has to be different (which is quite normal during imports)

I will try to update this post with a test script emphasizing my theory... or you can just have a look into Exporter.

HTH.

PS: considering your *coughing*: compilation is a two phase process, the package-declaration is done before BEGIN is executed, hence the output of B::Deparse is correct.¹

edit

just realized that tobyink++ practically gave the same answer. :)

update

¹)

> perl
package TST;
BEGIN { $a=42 }
package main;
print $TST::a;
__END__
42
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