my %hash;
foreach my $i ( 0..$#array ) {
   foreach my $j ( @{ $array[ $i ] } ) {
      $hash{ $j } ||= [];  #need to set this if not made
      if ( ! grep { $i == $_ } @{ $hash{ $j } } ) {
         push @{ $hash{ $j } }, $i;
      }
   }
}
my @matches = grep { @{ $hash{ $_ } } > 1 } keys %hash;