Add

/opt/local/lib/perl5/site_perl/5.8.9
[download]

instead of

/opt/local/lib/perl5/site_perl/5.8.9/LWP
[download]

to PERL5LIB. Then @INC will include /opt/local/lib/perl5/site_perl/5.8.9, and perl should be able to locate the LWP/Simple.pm module file when you use LWP::Simple;