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.

And you can pass them either "flat" or by reference:

# flat:
mysub(@array);
mysub(%hash);

# by reference:
mysub(\@array);
mysub(\%hash);
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See also: perlintro, perlsub, perldata, perlreftut

my %data;
my $myObj = new test::mod1();
%data = $myObj->prepare(%data);

-------------------------


package test::mod1;    
sub new
{
    my ($class_name, $dql) = @_;
    my $internalData = {dql => $dql};
    bless($internalData, $class_name);
    return $internalData;
}
sub prepare
{
    my ($internalData, %record) = @_;
    return %record;
}
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this is working... but i don't know how.. constructor how works ???

For constructors see perlboot.