I use libapreq under Unix. I've installed it using CPAN.pm, it is libapreq 0.31. Maybe it requires the script to run under mod_perl? I'm not sure, since all my scripts run under mod_perl, but the documentation seems to imply it, here's what it says for method new():

my $apr = Apache::Request->new($r);

I understand this to imply you need an Apache request object ($r) which you will only have available under mod_perl.

For further information you can check out the libapreq webpage which has links to mailing lists which might provide some help.