But please do not make passing on PERL5LIB a default.
Why? The PERL5LIB environment variable is set up after the fact (of changing $< and $>) of getting broader permissions via sudo.
Sudo is not only used to hand out superuser shells. It is designed to give limited access to a variety of actions in a precisely controlled fashion, most notably perhaps running scripts with privileges of a different user.
This can, for instance, enforce the use of a particular interface to some system service. To that end it is mandatory that the sudoer cannot change what code is being run via environment variables such as PERL5LIB. Therefore, caution would dictate not to undermine this safety feature through careless defaults. You can always be more specific where you have to.
I find it reasonable to play safe by default. You may resolve a certain incommodity the way you suggested, but should be aware of the security implications, too.