If you want uniqueness then just use the keys of a hash

my %hash = map { $_ => 1 } 'a' .. 'f';

$hash{b} = 'added'
  unless exists $hash{b};
$hash{g} = 1
  unless exists $hash{g};

print %hash;

__output__

e1f1g1a1b1c1d1
[download]

HTH

_________
broquaint