PS: by playing around with Devel::Declare is ought to also be possible to replace code like this:

my $foo = an(5, '$foo');
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With something more like:

annotated $foo = 5;
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Devel::Declare allows you to hook into the Perl parser to catch keywords and add custom parsing for them. In this case, you'd catch the keyword annotated and rewrite it to something like:

annotated(); my $foo = Scalar::Annotated->new(0, '$foo'); $$foo = 5;
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Thus people could use annotated in much the same way as they currently use my, local or our.