Not as dynamic, but you might want to setup a hash of method => coderef and have the implementation modules register therein.

package Wireless::Auth;

our %methods;

...

package Wireless::Auth::Wisc;

sub Wisc { ... }

$Wireless::Auth::methods{ 'Wisc' } => \&Wisc;

1;
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You could also wrap things up with a registerMethod routine rather than mucking with the hash directly. This way you can also use exists $methods{ $auth_type } to check what's been configured before calling $methods{ $auth_type }->( $user, $pass ) (warning for unknown methods and using a sub which always denies authorization).