use Data::Dumper;

my %h; # intial hash

# put in some random values
$h{'a'}{'1'} = 'z';
$h{'a'}{'2'} = 'y';
$h{'a'}{'3'} = 'x';
$h{'b'}{'4'} = 'w';
$h{'b'}{'5'} = 'u';
$h{'b'}{'6'} = 'v';
$h{'c'}{'7'} = 'r';
$h{'c'}{'8'} = 's';
$h{'c'}{'9'} = 't';

# make an assignment that I assume is by value
my %tmpHash = %h;

# make a change in the temp hash
$tmpHash{'b'}{'6'} = 'j';

print Dumper(%h);

print "\n\n\n";

print Dumper(%x);