Firstly to find @accessors, you can use the keys function on the %$self hash.

But I'd choose to push the value rather than the key so a loop over values(%$self) might make more sense.

my @tocheck;
for my $value (values %$self) {
  push @tocheck, $value if ref($value) eq 'ARRAY';
}

my %seen;
for my $array (@tocheck) {
  $seen{$_}++ for @$array;
}

return grep { $seen{$_} == @tocheck } keys %seen;
[download]

So far we haven't used map (but we did use grep), but we can combine the two loops together so we don't need @tocheck as an intermediate.

my ($n, %seen);
for my $array (values %$self) {
  next unless ref($array) eq 'ARRAY'; # we're only interested in array
+s
  $seen{$_}++ for @$array;
  $n++;
}
return grep { $seen{$_} == $n } keys %seen;
[download]

Here's a solution using map to replace one of the loops (Update: But it doesn't solve the right problem, since it just checks for duplicates, rather than things appearing multiple times):

my %seen;
for my $value ( map { ref($_) eq 'ARRAY' ? @$_ : () } values %$self ) 
+{
  $seen{$value}++;
}
return grep { $seen{$_} > 1 } keys %seen;
[download]

--
integral, resident of freenode's #perl