( [ @array ] ) x @array ;

##</code><code>##

@array{ @array } = ( [ @array ] ) x @array ;

##</code><code>##

%array = (
           'c' => [
                    'a',
                    'b',
                    'c',
                    'd'
                  ],
           'a' => $array{'c'},
           'b' => $array{'c'},
           'd' => $array{'c'}
         );

##</code><code>##

shell> perl -le 'print keys %{{map {$_=>1} qw/a b c d/}}'
cabd