A powerset should always include the empty set. (The cardinality of the powerset of a set of cardinality n should be 2n.) Therefore, you can simplify powerset: 

sub powerset {
  my ( $car, @cdr ) = @_;
  my @cdr_powerset = @cdr ? powerset( @cdr ) : [];
  return ( @cdr_powerset, map [ $car, @$_ ], @cdr_powerset );
}

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I imagine that this means that only two states are needed in iter_powerset.

the lowliest monk

In reply to Re^4: Generating powerset with progressive ordering by tlm
in thread Generating powerset with progressive ordering by Limbic~Region

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