I'm writing a module that, from the constructor, will accept essentially named parameters, and I'm wondering which of the two common ways of doing so is preferred.

Should I accept a single argument of a hashref:

# new MyModule({arg1 => 'val1', arg2 => 'val2'})
sub new {
    my $class = shift;
    croak('oh crap!') if ref($_[0]) != 'HASH'
    my %args = %{$_[0]};
}
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Or should I cast all arguments into a hash:

# new MyModule(arg1 => 'val1', arg2 => 'val2')
sub new {
    my $class = shift;
    croak('oh crap!') if @_ % 2;
    my %args = @_;
}
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I've seen both techniques used in many places, but which one is generally preferred and/or considered better API design?