Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
First you extract the keys from the hashes into arrays, and then solve the uniquifying the array problem described above. For example:
%seen = (); for $element (keys(%foo), keys(%bar)) { $seen{$element}++; } @uniq = keys %seen;
Or more succinctly:
@uniq = keys %{{%foo,%bar}};
Or if you really want to save space:
%seen = (); while (defined ($key = each %foo)) { $seen{$key}++; } while (defined ($key = each %bar)) { $seen{$key}++; } @uniq = keys %seen;