The impending advent of perl5.10 is leading me to think about what I'd like to see in a perl5.12.

I personally believe that it's now late to add to this thread, but I'm trying with a few interrelated ideas off the top of my head:

• hash slices, such that %hash{@keys} has the same semantics of

  %{{ map { $_ => $hash{$_} } @keys }}
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• on a more daring basis, hash-like slices of an array, such that %array[@nums] has the same semantics of

  %{{ map { $array[$_] => 1 } @nums }}
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• on an even more daring basis, hash-like dereferencing of an arrayref, such that %{\@array} has the same semantics of

  %{{ map { $_ => 1 } @array }}
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So, to test whether $element is in @array one may check ${\@array}{$element}.

(Moreover, these "conversions" may be optimized under the hood.)