"Cannot find the location of RT.pm that defines $RT::LocalPath

I’m running Makefile.pm to install RTFM 2.1.40, and getting an error
message:

"Cannot find the location of RT.pm that defines $RT::LocalPath in: inc
/usr/lib/perl5/5.8.7/i586-linux-thread-multi /usr/lib/perl5/5.8.7
/usr/lib/perl5/site_perl/5.8.7/i586-linux-thread-multi

/usr/lib/perl5/site_perl/5.8.7 /usr/lib/perl5/site_perl
/usr/lib/perl5/vendor_perl/5.8.7/i586-linux-thread-multi

/usr/lib/perl5/vendor_perl/5.8.7 /usr/lib/perl5/vendor_perl .
/opt/rt3/lib /opt/lib/rt3 /opt/lib /usr/local/rt3/lib /usr/local/lib/rt3
/usr/local/lib /home/rt3/lib /home/lib/rt3 /home/lib /usr/rt3/lib
/usr/lib/rt3 /usr/lib /sw/rt3/lib /sw/lib/rt3 /sw/lib Path to your
RT.pm:"

I’m slightly crippled by not knowing Perl syntax. I do have an RT.pm,
and it’s in /opt/rt3/lib. If I type in either /opt/rt3/lib or
/opt/rt3/lib/RT.pm, I just get the same message again. Any quotes, other
wrappers, relative addressing required?

Would someone be kind enough to help me out? Thanks.