Using a value in a perl references hash of hashes:
############################################################

Using dumper modul:

print Dumper( %sophomorix_config{'ou'}->{'uni'}{'GROUP_TYPE'}......;


Taking a value out of a perl hash reference:

$group_type_new=$ref_sophomorix_config->{'ou'}{$school}{'GROUP_TYPE'}{$group_new};

(Dont forget: ->)


keys on reference is experimental   (warning)
############################################################
#    foreach my $sam ( keys $AD{'sAMAccountName'} ) {       # warning
#    foreach my $sam ( keys %AD{'sAMAccountName'} ) {       # warning
    foreach my $sam ( keys %{$AD{'sAMAccountName'}} ) {     # OK

keys on reference is experimental
# foreach my $section ( keys $ref_modmaster ) {        # warning
# foreach my $section ( keys %{ $ref_modmaster } ) {   # OK


Perl Debugger:
############################################################

# Make debugger usable:
apt-get install libterm-readline-perl-perl


--- hash of hashes ---

# print hash of hashes (or other complex Data structure):
x %sophomorix_config

# print part of complex hash (or other complex Data structure):
x %sophomorix_config{'ou'}
x %sophomorix_config{'ou'}->{'uni'}
x %sophomorix_config{'ou'}->{'uni'}{'GROUP_TYPE'}


--- reference to hash of hashes ---

# print reference of hash of hashes (or other complex Data structure):
x $ref_sophomorix_config

# print part of reference of hash of hashes (or other complex Data structure):
x $ref_sophomorix_config{'ou'}->{'uni'}
x $ref_sophomorix_config{'ou'}->{'uni'}{'GROUP_TYPE'}
