Thanks for both of your answers. My error was that I was testing only against 'HASH' while I should have given myself an out. Taking your answers a step further, when I apply all types mentioned for ref() at Perldoc.com as in the following:

#!/usr/bin/perl

use strict;

sub traverse($);

#my $hash = {
#    key0 => 'value0',
#    key1 => { key2 => 'value2' },
#    key3 => { key4 => 'value4', key5 => { key6 => 'value6' } }
#};
my  %hash;
$hash{key0} = 'value0';
$hash{key1}{key2} = 'value2';
$hash{key3}{key4} = 'value4';
$hash{key3}{key5}{key6} = 'value6';

traverse(\%hash);

sub traverse($) {
    my $r = shift;
    if (ref($r) eq 'HASH') {
        for my $v (values %$r) {
            traverse($v);
        }
    }
    elsif (ref($r) eq 'SCALAR') {
        print "SCALAR:\t'$r'\n";
    }
    elsif (ref($r) eq 'ARRAY') {
        print "ARRAY:\t'$r'\n";
    }
    elsif (ref($r) eq 'REF') {
        print "REF:\t'$r'\n";
    }
    elsif (ref($r) eq 'LVALUE') {
        print "LVALUE:\t'$r'\n";
    }
    elsif (ref($r) eq 'CODE') {
        print "CODE:\t'$r'\n";
    }
    elsif (ref($r) eq 'GLOB') {
        print "GLOB:\t'$r'\n";
    }
    else {
        print "unexpected value:\t'$r'\n"
    }
}
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I get the following unexpected (at least to me...) results:

unexpected value:       'value2'
unexpected value:       'value0'
unexpected value:       'value6'
unexpected value:       'value4'
[download]

How is this possible if I have accounted for all possible types? Thanks.