I would not recommend a parallel port, there is more to it than just reading an on/off signal. Use a joystick port it's the simplest way to get analog or pushbutton data into a PC (trust me I have spent days figuring this out).

As to your question, Device::ParallelPort::drv::auto says to do:

use Device::ParallelPort;
my $pp = Device::ParallelPort->new('auto:0');
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