I think that setting $PERL5LIB will do what you want, add the following to your profile (.login/ .tcshrc or whatever):

Alternately you can pass -I flags (for example by editing the shebang line in your scripts).

And finally you can modify @INC in the scripts before calling require:

    push(@INC,"/app/subapp/cpan");
    require Module97;
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If you can recompile and reinstall Perl that solution is a good idea, but if not there is more than one way to do it.