As an interesting side note, there's a bit on the Perl source code that uses %_ (as part of the obfuscated language tests.) Namely, take a look at: t/japh/abigail.t

For instance:

$" = "/"; split // => eval join "+" => 1 .. 7;
*{"@_"} = sub {foreach (sort keys %_) {print "$_ $_{$_} "}};
%_ = (Just => another => Perl => Hacker); &{%_};
[download]