my @a = ( [ 1,2,3,4,5] ,
          [2,3,6,7,8,9,10],
          [5,6,2,3], );

my @b = @{$a[0]};

sub intersect{    
   my (%union, %isect);     
   foreach my $e (@_) { $union{$e}++ && $isect{$e}++ }
   return keys %isect
}

foreach my $a_ref (@a) {
    @b = intersect(@$a_ref, @b);
}