Ensuring uniqueness is quite easy, but you definitely don't want to concatenate. It sounds like you want a HoHoHoHoHoA.
See: perlref and use Data::Dumper to make it easy to see the deep structure of your variable via print Dumper \%hash.

For a config type example:

my %config;
my $inDir = $config{directories}{input};
my $tempDir = $config{directories}{temp};
my $outDir = $config{directories}{output};
my $bgColor = $config{colors}{background};
...
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