$tar is an object. Generally, perl objects happen like this:

sub new {
        my $self = {};
        [...]
        bless($self);
}
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$self is declared as a hash reference, and returned as a "bless'd" reference -- that is, an object. Qv.

http://www.perl.com/doc/manual/html/pod/perlobj.html

So you have to use "object", aka. "indirect", notation with it:

$tar->{key};
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This is distinct from, but similar to, the syntax for calling a method, which is a function in the module.

$tar->method();
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