Normally, you'd pass a reference to the data structure, unless you want it flattened.

# for hashes

my %hash = ( ... );
my $hashref = { ... };

# pass references:
MyModule::function(\%hash);
MyModule::function($hashref);

# pass keys/values as a flattened list:
MyModule::function(%hash);
MyModule::function(%$hashref);

# for arrays

my @array = ( ... );
my $arrayref = [ ... ];

# pass references:
MyModule::function(\@array);
MyModule::function($arrayref);

# pass elements as a flattened list:
MyModule::function(@array);
MyModule::function(@$arrayref);
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When you flatten the hash/array, you'll get its entries as separate elements in the function's @_. Otherwise, there will only be one element in @_ holding the reference.