Is this really the vendor's (Sun presumably) version of Perl or has some well meaning person at your place of business built perl 5.6.1 improperly and then naively replaced the vendor's version? It's hard for me to believe a vendor would build a totally broken perl.
Hopefully this isn't a multiuser machine, since security wise this will be a nightmare.
It's an application vendor, not Sun. All the scripts in the application use -I to load modules... It wouldn't suprise me if they did it on purpose to keep people from using "their" copy of Perl that ships with their application.