To use R3.pm you need RFCSDK from SAP AG. If you have legal access to an R/3 system you should be able to obtain it; if not, you should not use R3.pm anyway. RFCSDK is available on the Frontend CD and/or (depending on OS and R/3 release) any sapserv server.
If you don't know what Perl, SAP R/3 or the RFCSDK is, you probably have no use for R3.pm.
Download and install R3::rfcapi first and then R3.pm!
R3-rfcapi-0.32.tar.gz (12600 bytes) (R3::rfcapi version 0.32) R3-0.31.tar.gz (6549 bytes) (R3.pm version 0.31)