my @alphabet = (('a'..'z'), 0..9);
my %collection;
for (1..30) {
  my $len = rand(11) + 10;
  my $key = join '', map {$alphabet[rand(@alphabet)]} 1..$len;
  $collection{$key} ? redo : $collection{$key}++;
}
print join "\n", keys %collection;
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