Is there a way to do this without the intermediate %hash variable?

my %hash = map {$_ => ['id_1']} @array;
my $hashref = \%hash;
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can be written as

my $hashref = { map {$_ => ['id_1']} @array };
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Curlies create a hash, initialize it with the list in the curlies, and returns a reference to the new hash.