use Modern::Perl; my %ref_chain = ( 'key1' => { 'key2' => { 'key3' => 'not a reference' } }, 'key4' => { 'key5' => 'no ref here' } ); sub traverse_hashes { my $hashref = shift; foreach my $key (keys %$hashref) { if (ref $hashref->{$key} eq 'HASH') { say "$key is a hash ref. Recursing."; traverse_hashes($hashref->{$key}); } else { say "$key is not a hash ref (value: $hashref->{$key})"; } } } traverse_hashes(\%ref_chain);