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...
# populate your %project
...
   my $sub_project = $project->{...}->{...};
   etc.
}

my %multi_level = (
      'foo'  => { 1 => 'A', 2 => 'B' },
...
my $part_two = $multi_level{foo}->{1}; # part_two is a 
# scalar, a copy of the value of $multi_level{foo}->{1}, 
# namely 'A'. Changing it will not change %multi_level

my $a = 'blah';
my $b = $a;
$b = 'foo';
print "$a\n";  # prints 'blah'
print "$b\n";  # prints 'foo'