use Win32::Event2Log::Reader;
use Win32::Event2Log::Wevtutil;

sub select_engine {
    shift; # throw away Event2Log object, unless needed/wanted

    my ($engine) = @_;

    my %engines = (
        reader  => sub { return Win32::Event2Log::Reader->new(...); },
        wrapper => sub { return Win32::Event2Log::Wevtutil->new(...); },
    );

    $engines{$engine}->();
}