What I worry about is that someone else may do something bizarre in their CPAN module (like putting something bizarre in @INC) which will break my code elsewhere (like code to check modules in @INC for changes under mod_perl). If all the magical things in perl could be safely ignored by people who choose not to use them, this would be less of an issue. For a real world example, see the recent problems on the Catalyst mailing list with YAML, which uses Spiffy and apparently modifies the way 'use base' works in other modules.